VK API returns empty response unexpectedly (Amazon)?

Question

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Good afternoon!
I ran into an unexpected situation - there is a script written in PHP that works on behalf of a certain user (group management) through an application that is allowed access - an access_token was received with a scope that includes offline.
Unexpectedly, safe api methods stopped working, for example, photos.getWallUploadServer - if you send a token, we get a void in response, if you don't send it - an access error, respectively.
From the local machine - api requests with a token return a normal response. Tried to change server ip - no result.
Has anyone come across?

Answer 1

Resolved: raised a tunnel on the server where the script is running, tried to call api from the browser through it - an empty answer. I tried to enter VK from the user on whose behalf the application was running - VK asked me to confirm the number, referring to the fact that I was coming from an unknown source. Confirmed - api earned.
All this is rather strange - for a long time the script worked, ip did not change, and suddenly - security block.

Answer 2

I had the same problem, only I was getting timeout when working through sockets. The problem arose somewhere along the way between my server and the VK data center. traceroute did not reach, broke off somewhere in the middle. Check the trace path.
In general, to avoid such problems, there is selectel.