Missing PayPal callback if use PayPal Standard Payment in Sandbox(debug) mode

My problem is that the paypal callback (url is specify in notify_url) after a successful payment suddenly stopped working without any changes in this part from my side.
I building a new site and it's currently under development. For 3 days ago the paypal callback worked without any problems, but 2 days ago it suddenly stopped working. No any system update or something like this was did from my side. On the checkout page, the PayPal html form contains the correct notify_url and all other data. Redirection to the PayPal and payment is successful but order is on the missing orders. Contacted with hosting support and they said that no any callback from paypal to my site last 2 days.
I tried testing with different credentials and on different servers with a clean system. Same issue.
Does anyone have a similar problem?

Check IPN in on in your PayPal account.

Check your IPN history.
https://developer.paypal.com/api/nvp-so ... perations/

yes, I already read that need to try to forcibly specify the IPN url in the pp account settings, although 3 days ago everything worked without it.
I specified the IPN url in the pp account settings and the IPN show as activated, but this did not change anything and the problem did not disappear.
The IPN history is empty on https://www.sandbox.paypal.com/merchant ... pn/history page.
https://www.paypal-community.com/t5/San ... -p/2928705
This is 1 year ago dispute on PayPal Community with same problem so this can be some PayPal issue that was fixed that time. Can anybody confirm that this is a problem on the part of PayPal again, please?

Issue was fixed from PP side