Inability to Mark-up photos in iOS 16.2.1

Hi JimmieMaccccc3

welcome to the Apple (user-to-user) Community.

Re: Inability to Mark-up photos in iOS 16.2.1

Wondering if you may have updated (or would like to) to the latest iPadOS version:

Updating may, or may not, make a difference to the situation you describe.

About iPadOS 16 Updates - Apple Support says iPadOS 16.5 is the latest,

Apple support has an article online to help with editing photos with iPad OS16

Edit photos and videos on iPad – Apple Support

Eg: says:

Write or draw on a photo

Tap a photo to view it in full screen.

✽ Tap Edit, then tap 

✽ Annotate the photo using the different drawing tools and colors.

✽ Tap (+) to magnify or add a caption, text, shapes, or even your signature.

✽ Tap Done to save your edits, or if you don’t like your changes, tap Cancel.

Re: "I noticed that some of the photos will let me mark them up with my pencil and some of them won’t and I would like to know why so that I can fix this mark-up problem"

Wondering if the difference may be between HEIF or JPG photos, \

and

whether converting the HEIF photos to JPG would make a difference for you ...

and

if anyone else in the community knows more than either of us do about this situation.

Eg: Perhaps a more recent model of iPad Pro is needed to work with HEIF photos

Using HEIF or HEVC media on Apple devices - Apple Support

All the best :-)