This is a licensing error.  What license do you have installed?  This means that you have used the allocated licenses for what you have an cannot back up any other VMs.  You need to purchase additional licensing to complete the backups.

Here is a link to the KB for the first error

https://www.veeam.com/kb2439

The second one as Chris has stated is a license issue.  If you are using socket licenses how many do you have? and how many hosts/sockets are you backing up?  You have most likely exceeded that or are backing up from additional infrastructure that will exceed the limit.

At the top left click the hamburger menu, then licenses to see how many you have purchased. 

You can click the sockets tab at the top, then manage to see where they are being used. 

Hi @csaha77, both answers above are correct. If you wish to have a deeper understanding of it, here is a link for more information.

Hello,

You can find more information about the licenced host Viewing License Information:
More info : https://helpcenter.veeam.com/docs/backup/vsphere/license_view.html?ver=120