Payplans requires a minimum of Payplans 3.7.1 to be installed on your site before you can upgrade to version 4.0.0

I have download de install program but i have this error: Payplans requires a minimum of Payplans 3.7.1 to be installed on your site before you can upgrade to version 4.0.0

I have version 3.5.2 Build 2, of PayPlans ReadyBytes in Joomla 3.10.6 working with a lot of customers.

I not have apps / payments gateways that are already deprecated in PayPlans 4.x
I not have any customisation done to my PayPlans 3.5.x

What i must to do ??

Thanks
Joan