The message is null or exceeds 32 KB in length.
The user ID is invalid.
A timeout occurs when sending the peer-to-peer message. The current timeout is set as five seconds. The current login timeout is set as six seconds. Possible reasons: The user is in the ABORTED or RECONNECTING state.
The method call frequency exceeds the limit of 60 queries per second (channel and peer messages taken together).
The sender fails to send the peer-to-peer message.