Hi @LuIs DP ,
Per my test it works well to run following pnp powershell as a global admin:
Connect-PnPOnline -Url https://tenant.sharepoint.com -Credentials (Get-Credential)
Add-PnPHubSiteAssociation -Site https://tenant.sharepoint.com/sites/NoGroup -HubSite https://tenant.sharepoint.com/sites/Communications
If you have multi-factor authentication (MFA) enabled, please connect to SharePoint with browser based login:
Connect-PnPOnline -Url https://tenant.sharepoint.com -UseWebLogin
Add-PnPHubSiteAssociation -Site https://tenant.sharepoint.com/sites/NoGroup -HubSite https://tenant.sharepoint.com/sites/Communications
As a workaround, we could associate a SharePoint site with a hub site in UI at site level and SharePoint admin center level:
Site level:
SharePoint admin center level:
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