Was working now not

I purchased this app some time ago and it was working well for some time.

Then it just stopped working for no reason. I didn’t check up on it now because I have been so busy.

So I set up the fb app and everything was working fine then the fb messenger button on the product page stopped working. It would try to log in then do nothing. The customer would then not be able to continue as I had it set to must tick. I have since unticked that.

I have checked the fb app and there is no errors on it but it is still not showing up in my product page or if it does it tries to log in but nothing happens. It puts me in a loop then and nothing happens.

I don’t know what happened or what I have done wrong and I would really like someone to walk me step by step through what I need to do and how to do it.

Could the support team please contact me asap!
Thanks for your help!