Check the PHP Version
Make sure your server is using the correct and updated/latest version, this can be done by checking your cPanel (for Linux servers).
If the above still doesn’t work, check your .htaccess
Sometimes the PHP version is also added there and make sure it has the same version as your server settings, it usually looks like this:
I have seen this in cases where a caching plugin was enforcing gzip compression but the server was not configured to support it.
So, disable the caching plugin or replace it or troubleshoot WordPress.
If it still doesn’t work, contact support.