Mine also started working today. Yesterday I disabled 'Fast Start', did a restart, and removed both TV's from Alexa. Today I re-enabled 'Fast Start' did another restart and bingo the voice remote worked again - the graphic when it's in use is now slightly different. I added my TV's back to Alexa and that also works again. Since yours started working without tweaking maybe it was a patch sent by Roku and mine would have been fixed without all the fiddling around.
Thanks for posting that it's all working again. I'd given up on it but have just tried it now - without doing a reset - and it's started working again!
Out of curiosity I just tried mine again having taken no restart action etc.
Alexa commands now work again!
System update status still shows last updated Dec 11th so must be something on another backend service somewhere maybe?
Just got home and turned the TV on and I'm back to 'Something went wrong'
Disappointing.