Bonita 6.5.1. Studio

Embedded portal suddenly stopped opening

I use Bonita BPM 6.5.1. Community Edition. Embedded portal that is launched from Studio for testing purposes suddenly stopped opening. Web-browser shows "ERR_CONNECTION_REFUSED". I have reinstalled Bonita BPM Studio but it did not help.

What could be the reason? What shall I check?

Thank you in advance!