Hi @Shri-6058
When it comes to term store, there are two types of term groups. We could only add global term group in SharePoint center > Content Services > Term store (here you could find all the term set created in the same tenant).
Or you could add site level term groups in private site which is not contained in public site:
If the term groups could not be applied to all sites, you could check that whether it is global term group.
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.