Question: How to Exchange Remote PowerShell Connectivity Limit
By default, Exchange Server allows a maximum of 18 concurrent remote PowerShell connections. If it is required, then you can increase the concurrent limit as per your company control panel usage & policy.
New-ThrottlingPolicy -Name ITStaffPolicy -PowerShellMaxConcurrency 50 -ThrottlingPolicyScope Regular
You can associate this new policy to the service account under which the HC application is communicating with Exchange Server
Set-ThrottlingPolicyAssociation -Identity HCEXCH -ThrottlingPolicy ITStaffPolicy
Restart Microsoft Throttling service
For a detailed reference, you can check MS Article as well.