Ciao ​@weiryone. Have you tried to use the refresh activity achievements tool? Please follow the steps below:

https://support.strava.com/hc/en-us/articles/216919597-Refresh-Activity-Achievements

Yes, tried to refresh activity and it’s still not showing.

Ciao ​@weiryone. Have you tried to submit a ticket?

So, when you say it's not “recognising your PRs”, what do you mean by that?

If it’s something like - it was a 10k run but Strava only shows 9.98, you can try using the “correct distance” feature (open the activity on the Strava website, then in the menu on the left, choose three dots, and then Correct Distance). That will recalculate the run based on Strava's map data and *may* bring you over the desired milestone. 

It’s also possible that the activity really was shorter and while Garmin rounded it up, Strava didn't. Here's some details: https://stories.strava.com/articles/explaining-the-strava-tax

Lastly - if it was a treadmill run, Strava won't count it. 
 

If none of the above helps, you'll need to be more specific about what you mean. Ideally add a link to an activity that should have been counted as a PR but wasn't.

You can submit a Support ticket but honestly, the waiting times are super long these days (someone has mentioned in another thread they've been waiting 4 weeks now), I wouldn't try that venue...

Jana_S thanks for your reply. So just to clarify, my segment PRs are showing but not my best efforts. Ie on the 15 May I did a 5km (5.02km to be specific) run in 33.12 (this was a PR) - it came up on my watch as a PR for the 5km, 1 mile and 1km but didn’t show any of these on my activity achievements (the little crowns). Also, when I looked at Best Efforts for that run it has my 5 km as 35.35. Then on the 18/5 I did an 8 km run, again, my watch said I did a PR in my 5km but didn’t show in my achievements and when I looked at best efforts it shows 33.53 (this is still not my best time). It seems that my best efforts are not adjusting. The only time it has shown a PR is in my 10km - not in the achievements but where it comes up say “you have just set a PR in your 10km”. I’m not sure how long it hasn’t been doing it, I just thought I wasn’t doing in PRs. I’ve tried to “reset activities”, log in/out but still not adjusting.

I think you might be seeing the difference between Garmin (assuming you are using a Garmin watch) and Strava.  Did you have any stops anywhere in those activities?  Garmin uses “moving time”, so will show that you got a PR in a 5k but is not counting any stopped/paused time.  When it loads to Strava, Strava will include any stopped/paused time in the calculation, using “elapsed time”, resulting in a longer duration for a set distance than what Garmin showed.  

Oh ok, that makes sense. I do stop at traffic lights in all my runs so that could be why and yes, it’s a garmin watch. Thanks for your reply, i’ll keep that in mind on my next run :)