Unknown error at install

[cienislaw]

I'm trying to get Mailchimp module working, but an unknown error occurs during install. For sure it didn't assign hooks, so I did manually. But there is a problem with new newsletter subscribers - they are not synced. Forced sync added new subscriber first time, then stopped working. Hard to say what is wrong as I don't see anything suspicious in logs and error console. any idea how to find out what is going on?