Caught in a loop trying to sign in to Windows Insider

My PC was signed in to Windows Insider Relese Preview channel and it was working fine, but one day it said it wasn't anymore, and instructed me to turn on optional diagnostic data, even though I hadn't changed to required data. So I went to Diagnostic & Feedback menu and changed to optional, and then tried to join the programme again, in the end it asked me to reboot the machine. After rebooting, it asks me to turn optional diagnostic data on again, and so on.

After a couple of reboots, it will get stuck when attempting to register my Microsoft account, like in the screenshot. I performed an in-place upgrade using an ISO of the same build (19044.1319), hoping that it would fix the issue, but no luck. Is there any way to reset or re-register Windows Insider, or some similar solution?

Open group policy editor:
Win+R key, then run gpedit

Navigate down the tree to Computer Configuration > Administrative Templates > Windows Components > Windows Update > Manage Updates Offered from Windows Update. Open Manage Preview Builds. Click on Enable, and then select the insider channel you want to be on. Make sure to apply.

The solution wasn't exactly that, but your reply helped me find the cause, thanks. Group Policy Editor wouldn't open, saying I didn't have the appopriate rights, so the fix was deleting the contents of Machine folder in C:\Windows\System32\GroupPolicy\. Also, I had to set that option to "Not configured", otherwise it would ask me to turn optional diagnostic data on, even if it was already on. Did that, selected the Insider channel, rebooted and voilà, all is working again.