Good day Carlee,
The error message "Cannot paste this image. Try different source" usually means that Teams cannot process the image from your current clipboard source.
As you did not mention whether you are using Teams desktop or Teams on the web, please try the following:
Option 1: Upload the screenshot as a file
Save the screenshot to your device.
Open the Teams chat.
Click Attach file below the message box.
Select Upload from this device.
Choose the screenshot and send it.
Option 2: Use Teams on the web
If the issue occurs in the Teams desktop app, sign in to Teams on the web and try pasting the screenshot there.
Option 3: Take a new screenshot
Create a new screenshot, copy it again and then paste it into Teams.
Option 4: Repair Teams apps
Open Windows Settings > Go to Apps > Installed Apps > Locate Microsoft Teams.
Select Modify or More options, then choose Quick Repair.

Reopen Teams and test again.
If the issue continues, run an Online Repair and test once more.
Please let me know if the issue occurs in the Teams on the web or the Teams desktop application.
Thank you for your patience and understanding.
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