Error 525 when accessing subdomain



I have a subdomain set up (on a different server to my primary server) and I also have SSL set up in cloudflare, with both the key and certificate files on both servers. The following is my apache2 default-ssl.conf file

	ErrorLog ${APACHE_LOG_DIR}/error.log
	CustomLog ${APACHE_LOG_DIR}/access.log combined
	SSLEngine on

	SSLCertificateFile /root/
	SSLCertificateKeyFile /root/	

and this is an example of the error I get in my ssl_engine.log file

[Thu Sep 27 12:46:27.912478 2018] [watchdog:debug] [pid 18237] mod_watchdog.c(565): AH02980: Watchdog: nothing configured?
[Thu Sep 27 12:46:27.912592 2018] [proxy:debug] [pid 18237] proxy_util.c(1785): AH00925: initializing worker proxy:reverse shared
[Thu Sep 27 12:46:27.912602 2018] [proxy:debug] [pid 18237] proxy_util.c(1827): AH00927: initializing worker proxy:reverse local
[Thu Sep 27 12:46:27.912636 2018] [proxy:debug] [pid 18237] proxy_util.c(1878): AH00931: initialized single connection worker in child 18237 for (*)
[Thu Sep 27 12:46:28.005898 2018] [core:debug] [pid 18231] protocol.c(1278): [client] AH00566: request failed: malformed request line

I have no idea why this is happening as it works on my main server.