Hi ​@Billion, if your profile and activities are public, would you please share your Strava profile link so that someone can try and have a look? Also - what time frame are you missing?

If your profile/activities are private and you wish to keep it that way, you’ll need to contact Support (as here at the community hub, we don't have access to user data): https://support.strava.com/hc/en-us/articles/216917777-How-Do-I-Contact-Strava-Support

I’m betting this member actually has two separate accounts, but doesn’t know it.  And he’s using both the phone and a GPS device, and they’re feeding the two accounts the same activities.  

​@Jana_S you know the answer to this:  Is there any spot on the mobile app that shows the user number like we see in the web profile URL?    

​@JBW-Florida ha, it might be it indeed - two profiles! However, I don't think that the user ID is anywhere in the app. BUT, if you open your profile in the mobile app, tap the “Share” button to copy the profile link, and then open it in a web browser - it will open the profile there and show the ID in the (redirected) URL! And that way you can compare those two IDs for sure 🙂

​@Jana_S   Thank you.  I wish this user well.  Off topic:  I’m going to open up a new suggestion to have the user number available at some spot in the mobile app, just to help in diagnosing these problems.  I want you to vote for that !

​@JBW-Florida I absolutely will vote for it! 👍🙂

​@Billion to verify the two profiles theory, would you please post two links here:

1. go to the mobile app > tab You > tap your profile picture in the left upper corner > tap the “share” next to the Edit button (in the upper part of the screen), copy the link, and paste it here
2. go to the strava website, open your profile, copy the URL from the browser's address bar, and paste it here too

This will help us to verify whether you accidentally have created two profiles as ​@JBW-Florida  suggested.