Welcome to the Lightroom Community. I'd love to help you figure this out. I'll need more info.
What version of Lightroom Classic, Lightroom Mobile (iPad), iPad OS & desktop OS are you working on? Has this started to happen recently?
Pause the sync on all Lightroom surfaces first & then log on to Lightroom Web (https://lightroom.adobe.com) on a desktop browser to check current Sync issues on the left part of the screen.
If there are any sync issues, click on them to know more, find the original for those images, and back them up safely before you empty the Sync issues from Lightroom Web. As long as there are sync issues on the Web, you can encounter trouble in syncing images & edits.
After following these steps, let Lightroom Classic & Lightroom iPad continue syncing for at least an hour & let me know how it goes from here.
One thing to be careful of is when you have the same image open in Classic's Develop and at the same time are editing on the iPad is that the different app sync at very different times and it is very easy to lose edits because of this. In the iPad it will only sync after you back out of the zoomed in view with the develop tools exposed and will overwrite anything that might have synced from Classic on the desktop. Vice versa the iPad app will miss any edits you make in Classic while it is in the develop tools tab. So it is important to not be in Develop view in Classic while you are editing on the iPad.