Garmin Connect doesn't seem to recognize the device

[altairrrr]

Using the default device (EDGE_830) and Zwift, the fit file is correctly uploaded to Garmin but Garmin doesn't recognize the device => this leads to the activity not counting towards Garmin challenges and the device doesn't show up in the Garmin activity page.

Not sure if it's related but I had a warning when the fit file was processed:

[13:11:32] WARNING Field id: 193 is not defined for message session:18. Skipping this field data_message.py:107
WARNING Record 3992, <fit_tool.profile.messages.session_message.SessionMessage object at fit_file.py:73
0x000001E521110830>: size (82) != defined size (83). Some fields were not read
correctly.

I'm using the latest version of the tool: 2.0.3

[jat255]

Can you please upload a copy of the FIT file that's not working?

[altairrrr]

2026-01-29-10-16-16.zip
Here is the fit file

[jat255]

I don't use Garmin challenges at all, so I'm not certain if this file works, but can you manually upload this file to your connect account to see if it works?

2026-01-29-10-16-16_modified.fit.zip

I think the issue has to do with missing serial numbers, but I'm still not 100% certain

[altairrrr]

Adding this fit file seems to resolve the issue, the device is detected on the garmin page and the activity counts towards Garmin challenges !

Will a pontential fix cover other garmin devices in the list (especially custom ones since the edge 1050 ID is not in the list when configuring a profile) or should I stick with edge 830 ?

[jat255]

Great! I'm going to push some changes in a few that should allow for better customization of which target device you want to use, which will include configurable serial numbers and include appropriate software versions, which I also think are required for Garmin Connect to accept the files as "legitimate". It will also update the device list to include more recent devices, which are not supported by fit_tool (the underlying library I'm using for the file editing) since that library is quite outdated.

[jat255]

@altairrrr this should be fixed in v2.1.1. Can you please give that a try and let me know if it's working for you?

[jat255]

@altairrrr just an FYI, I made a discovery today that the actual device serial number is more important to Garmin Connect than the device ID, which I think explains why support for the "extra" garmin connect features was a bit flaky. I've documented this here: https://github.com/jat255/Fit-File-Faker?tab=readme-ov-file#%EF%B8%8F-important-device-serial-numbers, but the gist is that you should use the new options in the --config-menu to customize the output to match whatever Garmin device you actually have.

As far as I know, there's no public documentation of how serial numbers map to specific Garmin devices, so the safest bet is to simulate a device (and it's S/N) that you already have.

[altairrrr]

@jat255 Thanks for the heads up. I'll test probably tomorrow, however I just upgraded to the latest release and trying to configure the serial number of my edge 1050: it says Must be a 10-digit number between 1000000000 and 4294967295 , but the serial number of my 1050 is 9 alphanumeric characters. It's impossible to customize the serial number in the current state.

Update: My Fenix watch is also 9 characters (only numeric in this case)

[cagnulein]

You have to use the unit ID not the serial number. They are 2 different things Roberto Viola

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@cagnulein I have already warned you once #27 (comment) about using this repository for advertising services. I appreciate your contributions to the conversations, but if this happens again, I will have to block you from interacting with this repo. Il giorno dom 1 feb 2026 alle 14:06 Anton Milovanov < ***@***.***> ha scritto:

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*altairrrr* left a comment (jat255/Fit-File-Faker#51) <#51 (comment)> @jat255 <https://github.com/jat255> Thanks for the heads up. I'll test probably tomorrow, however I just upgraded to the latest release and trying to configure the serial number of my edge 1050: it says Must be a 10-digit number between 1000000000 and 4294967295 , but the serial number of my 1050 is 9 alphanumeric characters. It's impossible to customize the serial number in the current state. — Reply to this email directly, view it on GitHub <#51 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAALYWEYUBKHVBUGJEH33RD4JX25FAVCNFSM6AAAAACTJUXIRKVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQMZRGAZDEOJWGI> . You are receiving this because you are subscribed to this thread.Message ID: ***@***.***>

[jat255]

@jat255 Thanks for the heads up. I'll test probably tomorrow, however I just upgraded to the latest release and trying to configure the serial number of my edge 1050: it says Must be a 10-digit number between 1000000000 and 4294967295 , but the serial number of my 1050 is 9 alphanumeric characters. It's impossible to customize the serial number in the current state.

Update: My Fenix watch is also 9 characters (only numeric in this case)

@altairrrr Yes, this is a bit confusing I'm just realizing. cagnulein is correct in that it's the Unit ID we want, not the Serial number. What's a bit misleading is that the field in the FIT file is called serial_number, which you can see in a tool like https://www.fitfileviewer.com/:

Contrast that to what is shown on Garmin Connect (web) that shows an alphanumeric serial number:

The Android Garmin Connect shows the Unit ID in the System -> About page:

I'll update the documentation to make this more clear.

[jat255]

@altairrrr I've updated the docs in #68 and pushed a new release in 2.1.3 that clarifies this distinction in the configuration menu. Thanks for pointing out the confusion.