Let's see... So, no ability Galarian Weezing can have can make Boomburst fail. Neutralizing Gas nullifies any abilities in battle. Now, onto Weezing's moveset. Being a wild Pokémon it has to have Toxic, Belch, Self-Destruct and Sludge Bomb. None of these moves can cause Boomburst to fail. Now, we have determined that nothing Weezing can do can make Boombust fail. Now, this leaves a few options I can think of.
- You transferred the ability Soundproof to the Weezing. As Boomburst doesn't affect Pokémon with Soundproof, this could be why.
- You used the move Trick-or-Treat on the Weezing. This makes Weezing a Ghost Type and as a result, it lets Boomburst Fail.
- You accidentally used a Dragon Type move twice. Now, this may be unlikely, but still possible.
- You got really unlucky and missed twice in a row. This wouldn't cause the move having no affect though.
These are the reasons I can think of that are plausible. Hopefully this helps. Please comment if you find any other reasons. Other than this, it could be a glitch or a result of using 3rd Party software. I am not an expert on that, but it could be. If it is a glitch, it is currently not documented anywhere.