I still have the full selection of postal services, I'm on a laptop using Chrome. Which device are you using, if the app or mobile browser might be worth switching for now, if you can to a PC / laptop with Chrome.
Or have you selected the Simple Delivery option ? Could this be the cause?
When creating a new listing here's how to opt out:
Click on Custom Postage option, this is next to the simple delivery option on the listing on the right hand side, and it should allow you to then select your postage options.
The above is when using a PC / laptop sorry I don't use the app but imagine it must be in a similar place.
This link explains eBay's Simple Delivery:
https://www.ebay.co.uk/sellercentre/postage/simple-delivery?mkevt=1&mkpid=2&emsid=0&mkcid=8&bu=439
@leideb80
