Errrr It's abit confusing at first and I have to open your error_log to find out what caused the error and found that the error is because you entered 'auto' in the width and height of thumbnail settings
![:D :D](/media/kunena/emoticons/e-laughing.png)
The width and height of thumbnail must in numeric number. It will be resize automatically by css so you don't need to add 'auto' there
![;) ;)](/media/kunena/emoticons/e-wink.png)
https://www.dropbox.com/s%2Fk97jtdmkhhfwlvy%2Fmonosnap%25202021-05-02%252012-59-28.png?raw=1