So, I've spent hours trying to fix this by now, but have to admit I need support.
After mesh baking the high/low models in InstaMat, this is what ends up after baking. I've tried fixing scales, UV maps etc. I hope there is a smarter person out there that might point out what I'm missing here. Been following every step closely.
The crystal is not my biggest concern, but the handle.
Can you go back to Blender and share a screenshot of the UV's with all the objects selected in edit mode.
I'm confident that is where the issue lies, however it is hard to be precise without further investigation.
It could be a number of things..
Like incorrect object was selected when baking, incorrectly scaled object, etc..
Anything you already tried will need to be re-baked and re-exported.
Here's the blend file in question: https://drive.google.com/file/d/1b-kOsUhjKO7WLUOrRDdehHD4g1UbzFMN/view?usp=share_link
Here is an outline of what I found and posted on Discord...
You mentioned checking scales, if you changed any, a re-unwrap and re-export is required to fix the issue when importing to InstaMat.
Check your Normals too.
The UV's show no obvious error, however it looks like you have mixed up the mid poly backups and the low poly models.
Move the mid poly objects to the low poly collection and the corresponding objects to the mid poly backup collection.
Remember: After making changes in Blender you will need to re-unwrap and re-export before going back to InstaMat and re-importing.
let me know if this fixes your issues.