Yeah I'm having the same issue on Strava Android app: when I try to turn it on, the following error message appears, "Something went wrong. Your heatmap failed to load. Please try again later."

Hi @RussjGrant & @Joeharding, 
Thanks for your posts and sorry for any trouble you are experiencing. First, please be sure that your app is running the most recent version. If it is, next, please delete and reinstall the Strava app. Our recommended instructions are below:

1. Delete the Strava application from your phone
2. Power your device off for 10 seconds
3. Turn your phone back on
4. Reinstall the Strava application 

Note: You will not lose any data if you do this since all data is stored on the Strava servers.

Google Play Store:
Strava: Track Running, Cycling & Swimming
How to update your apps on Android: Support - Google

Apple App Store:
Strava: Run, Ride, Swim
How to update your apps on Apple: Support - Apple

If this does not resolve your issue, please submit a support ticket and include screenshots or a screen recording of what you are seeing so our support team can further assist you. 

Same here, personal heat map fails to load, try again later. What gives??

I'm having the same issue.
When loading the heatmap from app (IOS), I get the message:
"Something went wrong. Your heatmap failed to load. Please try again later".
It has been like this since a week or so, and I have no idea how to solve it. Any help would be very appreciated.

I tried all of these steps, signed out of strava, deleted strava, restarted the old iPhone 14, reinstalled strava… still nothing. The app is broken. Please help!

Unfortunately this has not rectified the issue. I've submitted a support ticket, and will bring the solution, if any, back here because it seems like it's a common issue.

UPDATE:

👋 Hi All!
Thanks for posting about this. Our team has identified the cause of the "Something went wrong" issue on the mobile app and they have resolved this issue. 
If you continue to experience this issue, please force close the app and then toggle the Personal heatmap off and on from the Maps tab. If this does not resolve your issue, please submit a support ticket and include screenshots or a screen recording of what you are seeing so our support team can further assist you.