Issue: If you found an error while sharing an office 365 subscription or if the subscription says pending always.
Try the following workaround to fix the issue instead of sending the customer to chat support.
2. Find the invitation email in your outlook.com Sent folder.(Main MSA)
3. Right mouse click on the Accept button and select "copy shortcut."
4. Paste the shortcut into a new email message using your email client (not outlook.com) or forward the mail from sent mail box.
5. Send the new email to the person you want to invite.
6. The recipient can either click on the link in the email or copy and paste the link into a browser address bar.
Hope that helps.
Note: The share subscription email should be a Microsoft Account to get the Install button for office 365.