Set-PnPGroup : Group cannot be found

Goal is to create a site collection level SharePoint group with 'Read' permissions, and apply this group to each sub-site. This group should contain several members.

My code is failing on:

Set-PnPGroup -Identity $glbMGRConts -Owner $OwnersGroup

... and says Group cannot be found. Not sure why, the group exists, and this line to set permissions to 'Read' works:

 Set-PnPGroupPermissions -Identity $glbMGRConts -AddRole "Read"

#

$varURL = "https://company.sharepoint.com/sites/Sandbox"
Connect-PnPOnline -Url $varURL -UseWebLogin
#Grab global owners group$OwnersGroup = Get-PnPGroup -AssociatedOwnerGroup

#Create name for group$glbMGRConts = "GlobalMGRs"
New-PnPGroup -Title $glbMGRConts

Add-PnPUserToGroup -LoginName user1@co.com -Identity $glbMGRConts
Add-PnPUserToGroup -LoginName user2@co.com -Identity $glbMGRConts

Set-PnPGroupPermissions -Identity $glbMGRConts -AddRole "Read"
Set-PnPGroup -Identity $glbMGRConts -Owner $OwnersGroup

Function Get-Subsites() {  
    $subwebs= Get-PnPSubWebs -Recurse   
     foreach ($Subweb in $subwebs)  
    {  
       Set-PnPGroupPermissions -Identity $glbMGRConts -web $Subweb -AddRole Read
    }  
}   
Get-SubSites