Difficulties communicating with the cluster displaying cached information

Hi,
i’ve just installed Couchbase server 5.5 in my ubuntu 16.04 server.
I’ve setted up a cluster and teh admin account, but every time i login in the interface at :8091, after a few seconds appears a warning:

difficulties communicating with the cluster displaying cached information

and then it automatically logout.
Also, i noticed that my new node that i’ve try to create is still in “pending status”, maybe is something related.
What should i do?

Thanks in advance