I logged on both the standalone indexer and search head as admin with full rights I verified that port 8089 is open on the search head but I get the error when I try to add a search peer I'm using http://10.90.20.237:8089 and admin with the password (the same on both servers).
Hi,
There is issue with your peer URl :
Try this : with https
https://10.90.20.237:8089
Also make sure you are putting correct user name and password of indexer.
Try using telnet to connect indexer from search head:
telnet indexer_ip 8089