last step PayPal error

Hello, hope you are all fine!
I have been waiting for more than 3 weeks and there is no reply.
I am getting an error after the payment sent. (last step when buying hosting via WHMCS) That looks to be an error with a file path. Do you know how/where I can set it up?

/whmcs/paypal/checkout/subscription/verify/5?subscription_id=I-LS30MGV4HX2H&ba_token=BA-0WS77714FJ965991E&token=4YG18255XT475566K
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WHMCS\Exception: Invalid request. in /public_html/whmcs/modules/gateways/paypalcheckout/lib/PaypalController.php:0
There are 51 errors like this:
Stack trace:
0 [internal function]: WHMCS\Module\Gateway\Paypalcheckout\PaypalController->verifySubscriptionSetup(Object(WHMCS\Http\Message\ServerRequest))
1 /public_html/whmcs/vendor/middlewares/utils/src/CallableHandler.php(26): call_user_func_array(Array, Array)
2 /public_html/whmcs/vendor/middlewares/fast-route/src/FastRoute.php(96): Middlewares\Utils\CallableHandler::execute(Array, Array)
3 /public_html/whmcs/vendor/whmcs/whmcs-foundation/lib/Route/Middleware/HandleProcessor.php(0): Middlewares\FastRoute->process(Object(WHMCS\Http\Message\ServerRequest), Object(Middlewares\Utils\Delegate))

No way to contact them, if any idea will you let me know? Thank you so much!