Delivery and payment methods stopped working, what files are responsible for this in PRESTASHOP?

Question

Delivery

Help, friends, because the situation is not very good. The fact is that, most likely, after some manipulations with the files, the methods of delivery and payment refused to work. More precisely, he writes that "There are no available delivery methods", similarly about payment. All regions are configured. Everything was fine, but a day later nothing began to work.
The request is the following: could you tell me which files are responsible for payment/delivery in Prestasop. Even indirectly which files are relevant. The fact is that I will restore these files from an older copy and hopefully solve the problem.
ps I'm afraid to restore all files at once, I risk breaking the system, because the parameters in the file changed in other aspects.
Help, who does not mind spending a little time and writing the names of the files, I would be very grateful.

Answer 1

"No available shipping methods" may be displayed if there is no suitable price for the given shipping method, or suitable payment methods. Double-check the dependence of delivery on payment. That is, is there delivery for this price range.
The second is to play around with zones and regions.
Perhaps, somewhere in the delivery methods, for example, weight is indicated. And the shipping method depends on the weight.
Here is something.
Files:
\controllers\admin\AdminCarriersController.php
\controllers\admin\AdminShippingController.php
\controllers\front\OrderController.php
\classes\Carrier.php
\classes\Cart.php
Maybe that's not all.
Also, do not forget to check the account from which you are ordering. What country is set there.