Hi,
Thanks for reaching out.
My name is Godswill, I'll be happy to help you today.
I'm sorry you're experiencing this problem, you'll have to delete the shortcut which was synced before you can delete the old channel.
Kindly refer to the article in the link below for detailed guide on how to delete the shortcut and after that you can go ahead to delete your old channel.
https://www.techserviceguru.com/fixed-youre-alr...
The link above is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products).
Thoroughly research any product advertised on the site before you decide to download and install it.
Please be sure to let me know if you need more help as I'll be glad to do so.
Regards...
Godswill