500 – Internal server error

Hello,

I had Quform PHP on 3 sites, all working fine until October when form stopped working on 2 sites:
https://www.laser-measure.co.uk/contact/
https://tradesurvey.co.uk/contact/

Still works on 1 site:
http://www.agatec.co.uk/contact/

I added ssl to http://www.laser-measure.co.uk and http://www.tradesurvey.co.uk in October and wonder if this has caused the problem?

I’m getting a server error:
500 – Internal server error.
There is a problem with the resource you are looking for, and it cannot be displayed.

Do you think security certificate is causing a scripting error?

Many thanks,
Jane