Depending on the complexity of your on-premises SharePoint environment, some issues can arise during configuration. You will need to review these troubleshooting steps to help resolve issues.
Hybrid taxonomy language not found
When configuring hybrid taxonomy and content types, the SharePoint Online tenant must be configured with the same languages as the on-premises environment. If it is not, you'll need to resolve them before moving forward.
In this case, the local languages supported include English and French, while the target SharePoint Online tenant is not configured with French:
To resolve this issue, add support for the missing languages in the SharePoint Online Term Store.
Invalid content type name
When copying content types to SharePoint Online, you may run into an error regarding an invalid content type name:
To resolve this conflict, use the Remove() method on the $ContentTypeNames variable and rerun Copy-SPContentTypes.