Can you check whether all the bundles in http://localhost:4502/system/console are active or not?
If not, please try restarting your server once.
All the users/authors have read/write/Modify/Delete ACLs, Can you please help me in this issue
sometimes I'm getting the error like 407(Proxy authentication error) also
Please find the attachment for the error
"except admin" - do you mean that an admin user can edit the page? If this is the case, make sure that the rest of the users/authors have Read/Write/Modify/Delete ACLs
checking the error.log will provide more details on the failure.