Feel free to try out Square, but I'm going to be transparent in that any issue that you might be having with passing tokens from a front-end to your back-end for payment processing isn't necessarily going to be solved by switching processors.
It sounds like someone else mentioned that you might not be supporting Strong Customer Authentication (SCA). Additionally, just because you got a token and created a customer, doesn't necessitate that a transaction would be successful. There are many other factors that can cause a transaction to fail.
Sometimes the transactions fail for fairly vague reasons sent from the bank, so you'll just have a generic declined message. Your best bet is to attempt to root cause the reason for the failures with your processor. You want to find out if this is only for transactions with a particular bank, credit card network, etc...
If you're unable to root cause the failures with your processor, then that might be your actual reason for switching.
[EDIT] Not going to be linking out here, but you're always welcome to talk to engineers on our team in our community chat channel that is linked throughout our developer docs. Only adding this having seen an edit above regarding a desire to talk to an engineer.