I gave up waiting for a response on here and wound up factory resetting it. I made sure everything was backed up and unchecked the settings option so it wouldn't re-apply the show button shapes option. Not sure why that setting was grayed out, maybe one of the newer updates or something. But I'm now good to go to use themes again. Hope this helps you!!
I'm also having this problem, and have literally spent over the last week going through and turning on & off every single setting in hopes that it was some other strange setting that had caused the "show button shapes" option to become completely greyed out and unable to be toggled. But to no avail. It has been ever since the last update, and its frustrating me to no end, ESPECIALLY because I'm stuck on a gosh dang Christmas theme that I am so sick of looking at!!! I cant find ANY ANSWERS, and i really really dont want to have to do a reset . :( Im at my patience end. One other setting greyed out also is the "Icon Frames" option under the display settings? So they've got to be connected I'm assuming? I hope this gets resolved soon, any advice anyone? So bummed....
I couldn't download themes on my Samsung Galaxy S9 plus. Mandy recommended turning off the option under accessibility settings / vision to "show button shapes which makes things stand out". After doing this my phone started downloading themes.
Thanks so much for this post! I've been trying for days to download a theme! Ever since this last update, I haven't been able to change the background in my texts. The white background the new update gave us is hard for me to see because I too have low vision. I turned off the frames around the icons and downloaded my theme! Thanks again for your help! By the way, my phone is a S7 and I guess the update gave me the S8 test message app.
I couldn't download themes for a month. I tried the suggestions above nothing worked. it dawned on me that we had moved a month ago and and that maybe my address was wrong on my credit card. So I went and deleted the cards, re-entered them and I'm back to downloading themes.
@Mandy1 Omg thx u I just got my s10+ & I couldn't get ANY of my themes UNTIL I READ UR COMMENT... THANKKKKKK YOUUUUUUUU SOOOOOOOOO MUCHHHHHH. 😘 I hope ur doing much better in 2019..
I have the Note 10 plus 5g and I had the same issue. I backed up my phone throught Smart Switch and was ready to factory reset BUT saw the ability to RESET ACCESSIBILITY SETTINGS. I did that and restarted my phone and I was able to download and and apply themes again.
1. Swipe down from the top of the phone and select the GEAR OPTION
2. Search RESET ACCESSIBILITY SETTINGS
3. FOLLOLW THE STEPS TO RESET
4. RESTART PHOINE
***YOU MADE NEED TO HAVE ANDROID 9 FOR THIS OPTION, I AM NOT BUT IT WORKED ON MY NOTE 10+