First time verbal shutdown

My partner is currently experiencing what I think might be a verbal shutdown for the first time. Both of us are AuDHD.
After a very overwhelming and emotionally intense day yesterday, they suddenly couldn’t speak. They understand everything, can communicate by typing, and are otherwise completely themselves. They just can’t get any words out.

I’ve read that speech shutdowns can happen with autism, but because this has never happened before, we are a bit scared. We’re keeping things quiet, communicating through text, and I’m not putting any pressure on them to speak.
For those of you who experience verbal shutdowns:
Have you ever had one last this long?
What helps you recover?
Is there anything I could do that genuinely helps?

They’re otherwise okay: fully aware, they understand everything and can write without any issues.
I’d really appreciate hearing about your experiences. I know everyone’s different, but I’d like to support them as well as I can.