sorry for my late response.
I have added a security deposit, here is a screenshot (Tour.png), what I have done.
Now after updating to WordPress 5.5.1, in the booking confirmation, the browser stuck, in URL http://kyklomartravel.webvisionaries.gr/booking-confirmation-tour/?booking_no=8858&pin_code=6955 with booking no and pin code. I tried to make a test with the tour on the screenshot and now in the confirmation the spinner is loading without any result! I choose to go to PayPal, so it happens because of the PayPal key? If yes could you confirm that or is another reason, which need to look at? In that case, could you help me?
It curious, because the browser console doesn't contain any error.