I am a Builder, Modeler, Scripter, Icon Designer and a Clothing designer,
I am having some problems with the clothing, I started yesterday and it says me that it had one problem and asked me: Did you use a Template?
I am a youtuber and I recorded how I made the shirt with Ibis Paint X (Phone) and it is made very good…
You could probably just resize the image in paint, re-upload, and you would be fine.
I wouldn’t recommend using phone apps to make clothing though because phones usually compress photos to save storage, so it was likely that you image on your phone is much smaller than the template’s size.
Used to be frustrated with this when I started making clothing. It is because your template is not the right size. Your template MUST be 585 x 559 in a .PNG format. No other sizes will be taken. I suggest using Paint.Net and create a separate layer for your design and one solely for the template and that must be at the very top at all times. As well as the boxes must be transparent.
This info could also help you as well, @Techyfied