Did you actually purchase the ink cartridges for your Epson printer, making sure that they were the exact type, because your supplier should be able to offer this advice, if you are not sure.
What you have described or suggested, then it looks like a wrong type was supplied, so go back to your supplier.
Cartridges can have a slight modification, and a typical example is with re-badged Dell printer's that might have been manufactured by Lexmark. With the Dell, the cartridges might have a slight plastic lug, where the Lexmark does not. Dell want you to purchase 'their product' and no other.
Here are some that should fit your printer click here