I’ve taken a look a the file, but can’t see anything obviously wrong, and the fact it works in WAMP and MAMP fine suggest that it should be okay. Heroku is picking the app up as PHP and using Apache automatically, but even when explicitly stated it makes no difference. Interestingly, I have seen what happens when .htaccess isn’t picked up, and it’s not 500 errors, the default page works fine but no others. So I’m not sure that is the issue, I’ve also compared my .htaccess file to the one here (https://github.com/martylouis/grav-heroku/blob/master/.htaccess) which according to the title and description is an attempt to get Grav working on Heroku, mine differed so I made it identical, still no joy.