Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
A current version of H&B or one now out of support or about to go out of support? If so perhaps the latest suite, that includes Pub, might be more cost effective
It is H7B 2019 ESD,
the client already paid for this and activated it. It is a recent purchase, but afterword's the client realized they need Publisher as well. So how does someone in this situation get access to Publisher? I can not imagine that the H&B License should be throw away, money down the drain, just because the client needs Publisher as well.
You can purchase Publisher as a stand-alone product directly from Microsoft: