A partner at a different organization invited me to join a Team. I can't access the account--the issue:
1. Clicked invite to join Team created by partner
2. Signed in to Teams using my Office 365 Premium account (joined to my business domain)
3. The Team doesn’t display under the ‘Teams’ section
4. The notification next to my account name tells me I have six new alerts/messages (I also received six email alerts stating I’ve been tagged in a discussion in the Team I was invited to)
5. When I click on my account name, it show me an alternate account I didn't create called 'Microsoft (guest)'. The notifications are attached to this account, not my primary business account. T

6. When I click on the 'Microsoft' account, I receive a pop up: “Want to switch to Microsoft? We might ask you to sign in again.”
When I click Yes, Teams refreshes, auto-signs me back in and loops back to the same alert (step 6). From then on, I’m stuck in the same loop.

Description: Guest users who have been removed from a Team still appear as search results when trying to add someone to a meeting.

Repro Steps:
1. Add a guest to a team.
2. Start a meeting. In the 'Invite someone' search of the Participants pane, enter the first letter of the Guest's name find the Guest and invite them to the meeting.
3. End the meeting.
4. In 'Manage Team', remove the Guest from the team.
5. Repeat Step 2. You will see that the Guest still shows up in the list.

This same issue also appears in the 'Search or type a command' bar at the top of the application. However, the @mentions do not have this issue and do not show the removed user.

Platform: Desktop app [1.1.00.28562]
Browser: [Issue also occurs in Microsoft Edge]
Device Type: Windows 10 Pro

Background: When setting up Teams, we accidentally added a number of our Team members as guest accounts. We realized the mistake, removed their Guest accounts, and added them as Team members. However, we still see the Guest accounts when trying to add users to a meeting.

In the attached image, the Guest account (top) has been removed but is still appearing in search.

On my account, I have access to several guest Teams. MFA is enabled on my account. For no reason, access to one of those guest Teams doesn't work anymore (used to work); switching to other Teams works. The process (and what it should be):
* My Teams/other guest Teams: Logon > MFA approval dialog > Approve on phone > Default team shows > Switch in app > app shows Team selected
* Problem Guest Team: Logon > MFA approval dialog > Approve on phone > Default Team shows > Switch to problem team > MFA approval dialog > no approval queued for phone, code doesn't work, etc. Can't bypass this MFA dialog which doesn't do anything.
Already tried disabling MFA, so now I have no (initial) MFA prompt, but for that problematic guest Team, I still get the MFA challenge which isn't an MFA challenge (no notifications pending).
This problem manifests in the same way on desktop client as well as iOS client when switching to that team.
Ideas/thoughts?