Newsletter broke my SSL? Site is going from down to active with no changes, strange issue!!

Hi all, 

I've added a newsletter to my blog page today and also created a pop-up, which I've now disabled. Since then my site won't load in Google Chrome. The error is below (I've also attached a picture to show this). 

NET::ERR_CERT_COMMON_NAME_INVALID

What is odd here, is that it came up on its own without me making any changes and then went down again. This has happened 3 times now, so the issue is intermittent. I'm making no changes to anything. As we speak it has just come back up after 15 minutes of downtime. I have not touched the SSL settings, which are set to on. This is failing on two devices so it's not my computers. 

Any ideas about what is breaking here? I think it could be something outside of my control. 

Site below:

https://www.innosee.co.uk/

Thanks, Tim

SSL common name errors and possible fixes.

Thanks but I can see no answers in that. This is dropping in and out today.