Attempting to create a new Site Recovery Manager (SRM) site pair fails with the following error:
“SRM server is already paired”
The error indicates that the SRM server at the site you are trying to pair is already paired with a different site.
The environment includes multiple vCenter Servers in Enhanced Linked Mode. For example:
VMware Live Site Recovery 8.x
VMware Live Site Recovery 9.x
An SRM appliance can only be paired with one remote SRM instance. In environments with multiple vCenter Servers (such as those in Linked Mode), attempting to pair the same SRM appliance with more than one site will fail.
If there is a requirement for a shared recovery site, where one vCenter instance needs to be paired with multiple other sites, a separate SRM appliance must be deployed for each pairing. Each of these appliances must be registered with a unique custom extension ID to enable multiple pairings on the same vCenter Server.
Please refer the below documents to configure a shared recovery site
Configure Multiple Site Recovery Manager Server Instances on a Shared Recovery Site
Connect the Site Recovery Manager Sites in a Shared Recovery Site Configuration
Note: In a shared recovery site, maximum we can have upto 10 SRM appliances