Photog-88 wrote: … Do I need to go to the Apple Store?
That's not a bad idea-- they can actually see what's going on. In Photos, every picture has very low resolution thumbnails, low resolution previews, originals, and maybe more. Macs keep more versions than mobile devices. It may be that the higher resolution images have been lost, or they might be disconnected from the database. People at the Apple Store may be able to sort this out.
Are you using Optimize Storage with iCloud Photos? If you're using iCloud Photos, you should go to iCloud.com and see what the pictures there look like.
I would also try selecting a picture and using Share>Export Unmodified Original and sending that to Files. See if that's a better version.
Are you running low on storage? What is your storage on this iPad? At Settings>General>iPad Storage, mine says 50.5 GB of 128 GB used. What does yours say? If it's more than 90% of the total, then that could be your problem