We wanted to let everyone know that we've recently found a compatibility issue that may be affecting studios using PlayFab multiplayer server hosting with an Unreal Engine 4.25 server. If you're using a UE4.25 server and you're having trouble getting your server running when hosted in Playfab (it will likely run locally without issue), the steps below should apply to you. You might actually be seeing an error that says "TooManyRestarts".
At fault is "Verify Peer" in the Unreal Network Settings. This needs to be set explicitly to true. In most cases, by default, it is actually left undefined (and hence will not have an entry in your INI files). To ensure the setting is correct, either add it to the INI directly, or toggle it off and then back on.
What's happening is that there are actually 3 states for this option. First, is "undefined", which is the default state. Next is "true", which is what you get when the lines are defined in the ini file, and set to true. Last is "false" which is defined as false. "undefined" previously defaulted to "true" under the hood, but that behavior has recently changed. It is now a distinct third case, which can cause issues when coupled with PlayFab server hosting. So if you toggle it to "false", verify the ini file changed, toggle it back to true, and then save everything, it should work.
We expect the behavior of this setting to change in a future Unreal Engine update, so please check back once you update beyond 4.25.
The readme in the GitHiub repo has been updated to reflect these steps: PlayFab/UnrealMarketplacePlugin: Source code for the PlayFab Marketplace Plugin for Unreal (github.com)