Can not update Skype and Telegram in my iPhone
Apple's stores are actually complicated layers of caching and edge servers, so the power off is a good way to get the phone to re-connect to a different "store server".

I would continue to do that or find a somewhat different network to try. For example, if you have another phone with a data plan - tether to that hotspot instead of using WiFi or find a different WiFi.

I don't think it's local to your device - but if you did suspect that still after exhausting the things you can control and waiting it out, you could back up the device and wipe all contents and settings. Then sign in and download only the two apps.

If you still have issues on a newly wiped device, then the store support team is really your next move. If that works, then you know it was a store caching setting - wipe the device again and then restore from the backup and things should be good to go.

Excellent notes and troubleshooting, I think you're close to a solution to these two apps not behaving in the store app for you.