Thanks for the advise.
First I tried with different versions of HybrdAuth, but of no use. Then I contacted one of the contributors of HybridAuth, he advised to download it from within OsClass market and try. Surprisingly, I can not find it on OsClass market anymore. Earlier it was there and I have used it around Sep/Oct 2016.
The problem is, I have switched to a new hosting provider and have to start from scratch. This time I am OsClass version 3.7.3, by the way is the new OSClass supporting Hybridauth? Please advise.
Thank you.