New OS and iTunes - no video file upload

[Expatriate]

This week I have upgraded my iPad Air OS to 11.3 and my iTunes to 12.7.4.74.

Syncing takes place from a designated folder on my PC hard drive. Some of the files in the folder are MP4s.
In the past these MP4s have uploaded to my iPad (which also created a special folder for them called Videos and copied them there) and played them without trouble. This no longer happens.

Do I have to set a flag somewhere? Is this an advancement in Apple technology? Do I need some extra software? What do I do?

Thanks

 

[Expatriate]

I installed VLC and uploaded the videos in question. All is well as far as that goes but I still don't understand why I had to. As explained in my initial post, iPad allowed for this in the sync operation in the past.

What has changed?
Why has it changed?
Can things be returned to the 'good old days' ?