I have been experiencing the same issue mentioned in this post: https://community.playfab.com/questions/68327/requesting-mp-server-in-short-time.html?childToView=69117#comment-69117 I am creating a new post for this question since there hasn't been any follow-up on that, and it seems that my comment was missed.
When I call the RequestMultiplayerServer server API on the client, I occasionally get the same error mentioned in the other post. I tried using CloudScript (Legacy) to call it instead, but it still doesn't always work - it just returns an empty result sometimes, instead of the error.
I am currently using 10 Servers Per Machine, and I have this issue even when only 1 or 0 of those are active and the rest are standby. I worked around this temporarily by having a loop run RequestMultiplayerServer until it succeeds, since after a minute or so it will eventually work again, but this can sometimes be a very slow and intensive solution.
Do you know of any reason why this error would happen when I am certain that I have standby servers available?