Depends how you define it, maybe. From 2004 to 2008 it was incredibly active and has been considered a “slow” eruption. It got a new lava dome and everything.

The big one was in 1980, but there had been active dome building up until 2008 with the occasional smaller eruption. I recall seeing a few steam plumes from Vancouver in 2004.

https://en.wikipedia.org/wiki/Mount_St._Helens#2004_to_2008_activity