This link will show you how to fix your problem so you can update the app catalog
1. For users of ALL webOS devices:
a. Open the “Date & Time” app on your device.
b. Set “Network Time” to Off.
c. Set the date to July 1, 2013.
d. Open the App Catalog
e. Type “App Catalog Update” in the search filed, and select “Enter” on the keyboard.
f. Tap the “App Catalog Update” app to display the details page.
g. Tap “Download for Free” to download and install the app.
h. Return to the “Date & Time” app.
i. Set the date back to the current date.
j. Set “Network Time” to On.
Note: Once the appropriate update is installed, the certificate is renewed even if the user later decides to reset the device (partial or full erase), or deletes any of the updates discussed here.
It is possible for users to install both an App Catalog update, and the “App Catalog Update” standalone app. Although not necessary and redundant, there is no harm in doing this.