WePay Payment tool: "Numerical values" error message is displayed.

On my current form there is a payment option with a drop down menu listing the names of months, but once someone tries to pay, there is an error code saying that the month indicator needs to have a # value. I couldn't figure out how to make the error code pop up but it says "only numerical values are allowed" or something like that.

I'm sorry for the trouble caused to you. I could not test your form as it requires valid credit card to make payment. I did clone your form and integrated it with my WePay test account and I see the issue. The issue seems to be related to "Suggested amount" you have added in payment tool. Please remove the "$" from the amount and that should solve your problem. Please check the screenshot below:

Once I removed the "$" from the amount, I was able to submit cloned form successfully. Please check the screenshot below:

Please remove "$" from the amount and that should solve your problem.