Hello Matt,
There is a known issue under investigation where some devices have trouble with the mobile app retrieving the watch list.
Please try uninstalling the app and then reinstalling it to ensure that you have the most up-to-date version of the app and then log back in to try again.
If the issue persists, please also ensure that your eBay Watch List contains no items that have already ended or are out of stock and try again.
If you have not already done so, please also file a support case from under the Help tab of the site so we can update you when more information becomes available.
- Craig