To regain access to your missing “legacy” contact list after the forced migration or upgrade to Teams in the Office 365 cloud, click on [ Go to Teams ] in the Skype for Business application and navigate to the Chat tab on the left hand pane. Note that you may have to sign-in (again) to Microsoft Teams.
Surprise surprise! The contact list is completely blank!
If you happened to click pass the dialog that appeared, you have definitely missed the important
“We’re importing your Skype for Business contact groups… This could take a while. To organize your contacts in the meantime …”
dialog box which exactly explains this strange phenomenon.
Depending on your Skype for Business tenant’s region, it can take several hours before your contact list finally appears in Teams itself.
For your convenience, note that your contact list is also accessible under Calls > Contacts.