This additional information is helpful.
It's important to understand that steam -- indiscriminately applied -- is evil (credit for that term to Chris Despos).
The reason your canvas bubbled is that "steaming" is not "pressing".
When you steam
a jacket, you're adding moisture. Moisture -- alone -- can (and, in this case, did) bubble the canvas.
When you press
a jacket, you're adding steam to relax the fibers and then using vacuum to extract the moisture. The application of moisture immediately followed
by vacuum to dry the fabric and canvas will cure the problem. Unfortunately, standard ironing boards don't have a built in vacuum.
I suggest that you take the jacket to a professional dry cleaner who knows what they're doing
. They should be able to fix the problem.
As regards the comment that you followed the advise found on SF and elsewhere, I'd respectfully disagree. What you've read is the conventional wisdom and, as usual, the conventional wisdom is always wrong.
The notion that you can "press" a garment with "steam" is a myth.
Learn more here: http://ravefabricare.com/wp-content/uploads/2016/03/43-position-papers-Steaming-your-fine-garments-01-SING.pdf