My first guess would be there is some problem with the OMSA agent. For 11th generation and older Dell servers, when there is a problem with the OMSA agent, the iDRAC connection may also fail. This is because on the11th generation and older Dell servers when testing the connection profile we first ask the OMSA agent to tell us what the iDRAC IP is. I’ve had to reinstall the OMSA agent before, but for you it’s affecting more than one server. That has me questioning the OMSA agent version being used.
What’s the hypervisor version (including upgrade) and OMSA version are you running on your different servers? Even though there is OMSA 7.3 out there, I want to verify you are running the right OMSA agent for your hypervisor.
The OpenManage integration for VMware vSphere release notes say which OMSA version is supported for different hypervisors: ftp://ftp.dell.com/Manuals/all-products/esuprt_software/esuprt_virt_solutions/dell-mgmt-plugin-for-v... --- Page 5, table 6. says ESX 4.1 requires OMSA 6.5. ESX 4.1 requires OMSA 7.0.
The release notes from OMSA 7.3 say it is supported on ESX versions 4.0U3 and 4.1U3, so it might work ok with the OpenManage integration for VMware vSphere, provided you are on that updated version of ESX. ftp://ftp.dell.com/Manuals/all-products/esuprt_software/esuprt_ent_sys_mgmt/esuprt_ent_sys_mgmt_opnm...
Hope this helps some.