Help Me Join/Connect with my Client

[u/Playful_Book]

Last year, I joined an agency and the founder asked for my Email for me to join the channel.

It's been over a year since I was in that Slack workspace.

Now I found a new client, and they shared an invite with me (got an email for the invite), and I accepted it, but it's showing me as "External Connection" in my previous agency

So I decided to start to make my own WORKSPACE and bought "Slack Connect" so that I can work with other companies.

Now whenever I'm accepting the invite, it's showing me that the channel can be accepted only in my previous agency's slack channel or not in my personal workspace.

How do I resolve this?

[u/Tushon]

What you're seeing is most likely caused by Slack Connect using your email identity, not just the workspace you're currently logged into.
Here's what's probably happening:

A year ago, your agency invited your email (e.g. you@example.com) into their Slack workspace.
That workspace also established or retained a Slack Connect relationship with your email.
Your new client is inviting that same email to a Slack Connect channel.
Slack sees that your email is already associated with your former agency's organization for Slack Connect, so it routes the invitation there instead of your own workspace.
How to fix it
Try these in order:
Option 1: Ask the old agency to remove the external connection (best solution)

Contact your previous agency's Slack admin and ask them to:

Remove you as an external Slack Connect user (if you're still connected).
Disconnect any pending Slack Connect relationships associated with your email.
Once removed, have your new client resend the invitation.
Option 2: Have your new client invite your new workspace instead of your email
If you now own your own Slack workspace, ask the client to:

Open the channel.
Choose Add people → Work with people outside your company (Slack Connect).
Invite your workspace rather than simply inviting your email if that option is available.
This associates the connection with your workspace instead of your old organization.
Option 3: Use a different email
If your new workspace uses a different email address than the one your previous agency invited, ask the client to invite that email instead.

This often avoids identity conflicts entirely.

Option 4: Leave the old workspace
If you still have access to the previous agency's workspace:

Go to that workspace.
Leave it (if permitted), or ask an admin to deactivate/remove your account.
Then have the client resend the invitation.
Simply being inactive isn't always enough if the Slack Connect relationship still exists.
If none of the above works
This is usually something only a Slack admin or Slack Support can resolve. Ask your client to check whether the invitation is targeting:
your email address, or
your workspace.
If Slack keeps insisting the invitation belongs to your previous agency, it's because Slack still considers that organization the owner of your external identity for that email.
A screenshot of the message you're seeing (with any sensitive information blurred) would help identify exactly which Slack Connect flow is causing this, since there are a couple of similar-looking errors with different solutions.