Changed eBay name and cannot connect app in Shopify

[etcshop]

Hi there

I changed my store/trading name on eBay recently and have lost connection to Shopify. 

I wanted to change my seller name on eBay and made the change, I found that it then disconnected my eBay app within Shopify. This all made sense so far. I tried to reconnect using the new name and the existing password which remained unchanged. Shopify would then not connect to eBay. I also tried the old name and password combination but that did not work as expected.

With the above not working I decided to remove the eBay app from Shopify and start again. I removed the application, closed down Shopify, then installed the eBay application again. Now when I click on the eBay app in Shopify I get the below error message

I am at a bit of a loss with this and would very much appreciate any insight or help anyone can offer me here. I have a fair bit of stock that needs manually updating which is causing a few problems to say the least.

Thank you in advance 

Dan