Issues with "TLS certificate verification failed" errors should check for and delete expired R3 cert from LetsEncrypt.

Windows users:

1. Open Run and type mmc.exe

2. Select <File>, <Add/Remove Snap-In..>

3. Choose <Certificates>

4. Select <My User Account>, and click<OK>

5. Expand <Certificates - Current User>

6. Expand <Intermediate Certificate Authorities>, and Click <Certificates>

7. Find the expired R3 and delete it.

NZBGet specific information can be found at https://nzbget.com/documentation/choosing-cipher/.