1. You have registered VCF Operations with the Business Services Console.
2. You have added licenses to VCF Operations after the upgrade from vRealize Aria Operations.
3. The new VCF Operations 9.0 can see your existing vCenters, which were running on 8.0.U3 then.
4. You upgraded the first vCenter to 9.0 and then assigned the license to it from VCF Operations 9.0 with no issue.
5. But the same action did not work on the other vCenter, with the error "Licenses could not be assigned to the selected vCenter systems."
Example of the error.
VCF Operations 9.0.x
vCenter 9.0.x
Workaround:
1. Log into VCF Operations 9.0 as local admin.
2. Go to Administration > Integrations, locate the vCenter adapter related to the issue.
3. Click on the 3-dot to the adapter and then click on "Delete", but DO NOT check the box of "Delete related objects".
4. Then click "DELETE".
5. Reconfigure this vCenter account by following Configuring a vCenter Account in VCF Operations.
6. Wait until the collection is green OK status, then proceed with Assign a Primary License to a vCenter Instance.
7. The license should be assigned to the vCenter with no issue.