Has your apache version changed recently?
I just got a 500 Internal Server error on my Godaddy vps and this is why, not sure if this will help you or not. (My other vps worked fine.)
I was doing a new processwire install, and Godaddy was missing pdo, and gd so I did an easy apache rebuild in WHM. Then the install.php file stopped loading and started throwing a 500 error.
I opened up cpanel and looked in my error log and it said:
.htaccess: Invalid command 'SetEnv', perhaps misspelled or defined by a module not included in the server configuration
I am planning on redoing easy apache and making sure the Env module is selected! I will let you know if that fixes mine!
What is bad, is it is suppose to start with your previous config, so I am not sure how this box gets unchecked! Could be a bug!
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Edit: Yes, checking the ENV checkbox did fix my 500 issue!