It seems to be working for me today too. Fingers crossed it stays working.

Thanks nniko. That page is very useful and I've not seen it before. It might be a bit out of date in terms of the names of cached folders etc on later OS versions. The principles are probably the same, though. Unfortunately, it didn't help and I'm still getting the same timeouts. Something weird is going on.

Hi filbercio Yes, I'm still down here too. I've been trying everything I can think of today and nothing fixes it - I get the same timeout error that you see above after about 1 minute, then a dialog telling me the app is damaged. I tried with a new sandbox test user, I tried it on Catalina, tried it on Big Sur etc. Lots of reboots. I tried using a different IP address through tethering to my phone. No different. I filed an item with the Feedback Assistant app - I wasn't sure what the right approach was. It's FB9048165 if that's useful. Please do let me know if you get any progress. Thanks

Yes! I thought I was going mad. I'm in the UK in case it is relevant. Since yesterday evening I haven't been able to coax my Mac app to generate a receipt when I do the usual exit(173). Nor have I been able to get in app purchases to present any store login dialog. Things just hang and eventually tell me that they timed out, or the app is damaged. I've created new sandbox users in case the ones I had been using had suddenly been destroyed by accidentally logging into production somehow, but that made no difference. I think I've lost an entire day on this now.