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.
We are most definitely listening. We appreciate the feedback and are always looking to improve our developer experience. Stripe has done an excellent job in that regard.
If you would be open to it, we'd really like to chat with you on your thoughts about our SDKs & documentation. Feel free to shoot an email to moot@squareup.com or message our Twitter @SquareDev.
I'm not denying it. Just that, when they started out, their response was telling: "How do you plan to run this 'awesome publishing platform' for free?" "Um ah we...ummm...magic? We'll see." I've seen that enough times to recognize digital sharecropping: first you work for free, then we monetize it for ourselves. Amazing that people dismissed that with "nah, they wouldn't dare. Why not? They're new, therefore not evil!" #wishfulThinking
I knew they had them, just haven't seen much enthusiasm behind them. I would think a large majority of Square's offline customers also take payments online and would imagine a small minority are using Square for online. The credit card processing APIs seem to get lost in all the rest of the POS/order mgmt APIs. And they're already on an incompatible v2 which doesn't really seem all that much better, just different.
There is a Block OSS Discord you can join to connect with folks to troubleshoot it (or just report something not working on the GitHub repo)