Background -- I have a Synology Disk Station. When setting it up, in order to make a secure connection I registered the Domain I planned to use with Synology and received a registered Domain Name. I then applied for and received a certificate from “Lets Encrypt. It worked fine for a few years. I was able to login to the Disk Station Locally using the Local Network IP I had assigned to it, and also able log in via the registered Domain through Synology with a Secure Connection using either method when logging in. Everything worked perfectly. Over a year ago I had some issues with my network (it has been too long ago for me to remember what it was). I could not resolve it, so when I called Netgear Tech Support they had me reset my router to factory settings. This did fix the issue I was having, but I later noticed resetting had changed my IP address. I thought this was not a problem at the time. It was then I also noticed I was no longer getting a Secure Connection on through my Disk Station. Have been trying to resolve this on my own, but I am not having any luck. But I am learning as I go. Present Day – I am still having issues logging in. The message I get when I log into the Synology registered Domain with Firefox is "Unable to Connect". I tried Chrome and get a similar message. When I log in locally using the assigned IP address I get "Warning: Potential Security Risk Ahead".

I click on the "Advanced" button where Firefox displays the Error Message:  SSL_ERROR_BAD_CERT_DOMAIN.  I continue with the exception and able to log into the Disk Station. 

My Goal is to get it working with a secure connection as it did before the Router Reset. -- I have checked all the appropriate ports are open. 5000 and 5001. -- Have checked for any firewall restrictions. -- I have tried replacing the previous certificate with a new one. -- Synology Tech Support does not seem to know, so I figure the problem lies within Windows 10 or Firefox. -- The Certificate in my Windows mmc Console says the Certificate is OK. Weather that is the one that is used for this connection I am speaking of, I do not know. -- The Certificate is current and has not expired. My apologies for this description being lengthy, I just want to make sure I state everything I can think of in order to get this fixed. I do not know a lot about this topic, but am learning as I go. Any help is very much appreciated.