Sent item using eBay returns label, no tracking no. from Post Office

[jtlsuk]

Hello, please help!

I started the returns process and printed out the Ebay returns label, I took the package to the Post Office but all they gave me is a 'Horizon Certificate of Posting Tracked Returns", with a bar code no, sellers address, and saying the package was accepted. It doesn't look like there's a tracking no.

What I'm confused about:

In the help section, eBay says it will automatically add tracking information once the package is posted if you use their returns label. This hasn't happend.

But in eBay's returns process, you have to mark as dispatched and add a tracking no. So which is right?

All I have is a bar code no, which was on the returns label. When I enter this as the tracking no, eBay says that "The tracking number you have provided already exists in our system. Please use a valid tracking number for this return." What does that mean??

Has anyone used this system before? Is there a tracking no I should have got in addition to the Certificate of Posting?

EDIT: So literally within moments of posting this I've got a message from eBay in my inbox saying the package has been marked as dispatched. What I think has happend is I tried slecting the courier as 'Other' NOT Royal Mail and wrote 'Post Office' and put in my bar code then pressed Enter. eBay still came back with an 'internal application error', but it does seem to have worked. Before I was selected 'Royal Mail' as the courier. This makes no sense to me, but isn't unexpected. Ebay has always been a very poor consumer experience.

EDIT 2: Even though the item is marked as dispatched, I'm not sure if it's actually being tracked in any system, or eBay has just updated with the information I entered. Well, hopefully my package will get to the seller.

EDIT 3: It seems Royal Mail's website on ebay reutrns has better information than ebay's own help section. It says I should have got proof of posting and a tracking no.