What would yoy do? with this issue

I am basically a retired cook and find scripting confusing – so please be gentle with me.
I am running 4.4 WordPress using MH Elegance lite
I have a problem
First ALL was working just great.
Suddenly (Cannot thing why) At first the “edit page” in administration (to any page) stopped working.
Believing this issue could be a plug-in (with a update)I isolated the plug-ins folder using FTP – still edit page would not open
Next using FTP I isolated each individual plug- individually – then reinstate plug-ins and discovered the edit page works – so it at first appeared, it could be a plug-in issue
I next went to plug in folder in administration to find the link (wp-admin/plugins php) returns “ This Page cant be displayed”
Catch 22 cannot open plugins to isolate individual to establish If, or which could be the problem
Next tried to update in dashboard (wp-update-core.php) still returns “This page can’t be displayed”
Then discovered, no links with (wp-admin/plugins php) or (wp-update-core.php) will open anything. All return “ This Page cannot be displayed”
I checked using FTP and find both files are there

Anyone has any ideas what I should do next
Please advise.