I am unable to add an alternate host.

[Dave_Neville]

The alternate host meets all the license requirements and prerequisites.   In past webinars this year I have been able to add this person, but at times an error message "only paid users can be added as an alternative host".

So, this issue seems to be intermittent, but I need to add this person to future Webinars.  

[Ray_Harwood]

Welcome to the Zoom Community, @Dave_Neville.

There are two requirements for an Alt-Host:

1. They must be on the same Owner’s account.
2.  They must be a Licensed (paid) account.

Based in this, with the Dell email address, I assume that Karl and you both work for Dell? And the fact that there was no error message indicating the potential Alt-Host was not in the same account, I’m assuming that Karl has a Basic account under the Dell organization’s Zoom account.  I’d contact your internal Zoom Admin and ask if Karl can be upgraded to be a Licensed user. 

If you don’t both work for Dell, let me know how the accounts are related, and I’ll see if I can help. 

Here’s a Zoom Support article that might be of some help:

https://support.zoom.us/hc/en-us/articles/208220166-Designating-an-alternative-host