I was having the same issue, but I was able to get the default text sound working. I thought maybe it was an issue with the texting app I use (Mood). Now it seems like it was due to the recent update.
At first all messages were only vibrating when coming in. There's a setting in the mood app that I enabled and sounds started working again. However, any customized text tones I set in my app for individual contacts do not work. All sounds come in to whatever I have set as my default sound. I also noticed that if I change someone's custom tone, it somehow changes that to the default tone and any messages that come in are now set to that tone.
It looks like they maybe changed the way notification settings are handled? It looks really different for me now.
When I get a text it comes up like this.
If I press and hold, I get these options (This is what's new, I've not seen this before the update)
When I click the gear icon to bring up advanced settings, this is what I see...(why so many?) I thought maybe they were tied to the last few people that texted me, so I did some testing. I had a friend text me and in the screen shot below, I noticed that it would highlight one of those 'messages' as you can see below....
So I pressed and held on the highlighted one that says 'messages (custom)' it brings me to the advanced screen (picture below) and in there are more options, one being 'sound' and all are set to my default text notification sound. I have tried changing just the highlighted one to something different hoping it would maybe change it just for that person, but it still changes it for all contacts.
*Edited* Last night I did try and reset app permissions as someone previously suggested, but that did not help unfortunately. I'm happy to have text time, just not happy my customizations no longer work.
Last edited: Feb 28, 2020