URGENT- JPGs/PNGs exported from Illustrator not accepted at Walgreens or CVS for priting

Hi!

I have an Etsy shop with downloadble prints. A few buyers have contacted in the past couple of months saying that they can't upload the artwork to be printed at Walgreens or CVS. The website says they are "too big".

All my files are around 1.5Mb and JPGS/PNGs. File requirements for upload are Jpg, PNG, PDF etc. Max size is 150Mb.

I don't know what's going on and why it's rejecting my files. Places like Fedex, OfficeMax etc does work.

These are prints made in Illustrator. Other prints that I've done in Photoshop do upload succesfully.

Please help! I need to fix this ASAP for my business. 

Thank you.