We have a problem now at customer side, when we have call in queue and agents, that should be ready to receive it, but they not received, because in Aux mode by some reason.

We added checking of agent state after each SetAgentState request and all looks good, so agent's shouldn't be at Aux mode.

What can be a cause of this problem?
What can have influence to workMode of agents? Could it be AutoIn workMode used in SetAgentState request?

Yes, workMode will affect the state an agent enters when a call ends. You can get a full description of the combinations in the "Set Agent State Service" section of the document "TSAPI for Avaya Communication Manager Programmer's Reference".

Martin

Note also that Communication Manager can be configured to automatically place agents into an Aux work state for a period of time after call ends.