Upgraded to anki 2.1.30 is not working

[mmdj2]

json.decoder.JSONDecodeError: Expecting value: line 1 column 1 (char 0)

re-install the the previous version that you had installed (2.1.26) on that version go to File -> Switch Profile and click on Downgrade & quit then install 2.1.22

the previous version that you had installed might not be 2.1.26
you can try installing the latest version or latest beta version and try those steps