I activate advanced sensors and attempt to barrel roll. I can't because another ship has blocked me. Because my barrel roll did not work do I have to take another action now or can I maneuver and then take a regular action?

Thanks for the help

If you declare an action and cannot perform it, you are free to perform another action, or no action at all.

In your scenario, you can choose not to perform any action with advanced sensors. You then complete your move, and are free to choose an action in your perform action step as normal.

X-wing allows you to backtrack completely out of a sequence if you want to. You would not be locked into having to take your action before your maneuver as you can even back out of Advanced sensors.

The similar ruling to this one is Dutch passes off a TL to Wedge so he can TL a lambda. He tries but finds out that the Lambda is out of range. The TL unwinds all the way back to Dutch so Dutch can choose the rookie now to get the free TL and TL up a Tie fighter. Wedge was not stuck with trying to TL something, the sequence came all the way back to Dutch passing off the free TL.

I've come up with a couple rule of thumbs for some things. I have "if it fits it sticks" for Boost,BR, and Decloak. For this it is "All the way out comes all the way back in".