I only just started using a trainer again after not using 1 for about a month & it opens n go's though the normal checks n the normal page shows then it just shuts down in 4 secs of opening.
I have done most the troubleshotting even got rid of my Avast n now have MS essentials & Malwarebytes anti-malware & winders defender is disabled (Windows 7 Ult 64bit)
& its all the trainers even the 1s that worked a year ago. Wot the heck is going on 😭
I have exactly the same setup as you, MSE, MWB and Win 7 and all the CH trainers work perfectly for me.
The one thing that might be a little different is the MWB-Anti-Malware product. I'm not sure which version you're using but I'm using the free version. That might give you something to check at least. Otherwise, as PWiz stated, something is blocking trainers on your end. Win 7, MSE and this MWB are all extremely accepting of CH trainers and I've gotten along that way for years without any problems.