[Symbiote]

They were probably optimistic, incorrectly. It's easy to think everything will work when you have a written guarantee from the government, and have never personally experienced a dysfunctional, authoritarian bureaucracy.

[MichaelZuo]

An invitation from a local official can not be a written guarantee of something beyond them?

It’s not even a guarantee of getting the relevant visa in time, that’s true for every big country I know of.