Hi Shadrach,
It appears that you server had some recent patch or security update or some recent changes which could be the root cause? Does your IIS stops as well?
I would request please validate the following things at server level.
1. Check all the IIS settings and security is in place.
2. Check Server certificates, also if your CRM applications certificates. Should not be expired or invalid.
3. Server Firewall. IP/ Port whitelisting and all.
4. Is your CRM using HTTP or HTTPS, in case on SSL, check TLS versions, it should be latest one.
5. Check server evet logs for any errors or warning. This would help why your application is stopping servicing HTTP request.
6. If your IIS setup on user principle, check service account as well, such as password policy should be set on never expiry, not locked by any other sources.
Try these troubleshoots and check if you can find any root cause to this.
Thank you.
Ganesh
