A message says "Unable to open the store. Please try again."

You tapped Update and SkipTube could not open the App Store. A message with the title Error says Unable to open the store. Please try again.

Nothing is wrong with SkipTube. The update is still waiting.

1. Tap the button on the message to close it.
2. Tap Update again.
3. If it fails again, open the App Store yourself. Search for SkipTube, or open your Apple Account in the App Store and look under the updates.

See How do I update SkipTube?