Ever since the last Android update my Samsung S7 Active is not recognised as an external storage device and now I cannot transfer videos to my PC. MTP keeps failing and Picture Transfer Protocol only recognises JPG Image files not mp4's. ??
Lets start here, first MP4s aren't actually image files. They are video files. So they would never be viewable as image files.
Now in regard to accessing the phone from other devices, it depends on how you are doing it.
First, try restarting the phone (just turn it off and back on). Then connect it to the computer via USB. You should be able to, from the computer, open up the "Internal" storage or the "External" storage (SD card) from the computer by opening it up as a folder. You don't need to use the manufacturers software. Just open it up as a folder like you would for any location on the computer itself. From there you should be able to move files back and forth from one device to the other.
When the system on the phone updated, was it an update that came through the phone's "Settings" or is this something you chose to install? If the latter, then it was not an update, and that could be your problem. If that is the case, I would uninstall it. If, however, it is the former, then you may need to see if any of the apps you have on the device are hindering what you are trying to do. Some have conflicts with phones after updates.
I am fully familiar with what you are saying, however this only occurred after the AT&T Release of the latest Android updates. The phone's MTP protocol fails and leaves me with only the option of Picture Transfer Protocol, hence not able to see MP4's (which I know are not Image files)...I have worked in IT for over 29 years now and this is definitely due to the latest Android updates AT&T release on it Samsung platform. I ended up downloading the Kies Air wireless app and was able to see my Video files via that...but I sure wish AT&T (or Samsung Android) developers would fully test their releases. This problem is rampant on may message boards out there now.
Ah the 'fully test software before they put it out' thing. Yeah. I have to agree with you on that one. It seems like lifetimes ago, but I was a tech support person for a 'former' big company (starting back in 1995), a beta tester for them and another software company at the same time. By the time I stopped working for them (one in 2000 the other 2005) I had had quite a 'few' discussions with those above me about more thoroughly testing software before releasing it. Alas, they seem to do it even less now. Kind of like using people as basically unpaid beta testers.