The error net::ERR_HTTP2_PROTOCOL_ERROR indicates a problem with the HTTP/2 network protocol. 

There are many possible causes and methods for resolving the issue. 

We encountered this problem on a website hosted by OVH, which prevented js files from running. 

To fix this problem, you need to modify the .htaccess file and add the following line : Header always unset Content-Length

# Various header fixes.
<IfModule mod_headers.c>
  # Disable content sniffing for all responses, since it's an attack vector.
  # This header is also set in FinishResponseSubscriber, which depending on
  # Apache configuration might get placed in the 'onsuccess' table. To prevent
  # header duplication, unset that one prior to setting in the 'always' table.
  # See "To circumvent this limitation..." in
  # https://httpd.apache.org/docs/current/mod/mod_headers.html.
  Header onsuccess unset X-Content-Type-Options
  Header always set X-Content-Type-Options nosniff
  #
  # custom code :
  Header always unset Content-Length
  #
  # Disable Proxy header, since it's an attack vector.
  RequestHeader unset Proxy
</IfModule>