Saucelabs plugin 5.7.1 and 5.7.0 do not work with Report Portal 5.7.2

[nowakoo]

I'm trying to integrate Report Portal with Saucelabs. I installed the latest version of the plugin, inserted Username, Access token and chosen the data center and I'm get the following error:

An error ocurred while connecting to server: Unclassified error [null]

This error message tells me nothing, as well as entry in network traffic that I attached:
Could you please help with the integration?
I am using Report Portal v. 5.7.2 and I tried Saucelabs plugin v. 5.7.1 and 5.7.0 (both showed the same error) - plugin-saucelabs-5.7.0-all.jar and plugin-saucelabs-5.7.1.jar from github