Hello @ericbakuladavis,
Thank you for your answer, I could finally solve the issue, it was due to a php file from the Redsys payment gateway which I had modified and was disturbing the whole woocommerce function. Now I have another problem, which is the bank redsys gateway not working properly, but that must be a problem of the bank gateway, and I hope they will be able to solve it.
Thank you very much for your help!