Same issue, new with the iPhone 12 Pro. I was using an 8 before, no issues. (Which is obnoxious... you'd think paying $1000 to upgrade from an 8 to a 12 would be nothing but benefits... but it's wrecked both my contacts / texts / call ID AND my Podcasts format--the two things I use most on my phone--so I'm kind of furious. I already traded in my 8 too and had it wiped clean (for a whole $80 off my new iPhone, so no reverting back. Also no one notified me that two-factor authentication required manually switching it WITH my old phone, so every single thing I use that requires 2-factor demanded that I disable it for 5 days and then reset to my new phone, including the ability to do ANY banking or send money... also infuriating.)
Anyway, as to this problem I feel like I've tried literally everything I can plausibly think of. I'm updated to the latest software (14.5.1).
Take 1) First I thought it was my fault, so I want to iCloud contacts and updated every contact to include a "1" before the number... didn't work.
Take 2) Then I tried the first "obvious" solution... went to iCloud on my phone, toggled contacts off from sharing, restarted the phone, turned them back on... no dice. The contacts came back, still no names.
Take 3) I tried turning iCloud off entirely, restarting phone, turning it back on. Also didn't work.
Take 4) I deleted my entire contact list from my phone, then went to my MacBook and restored them to mobile... nothing.
Take 5) I tried deleting individual text threads and then asking my friends to text me back to start fresh, was SURE that would work... nope!
Take 6) Figured I was on the very last option I could think off... I went into settings in iCloud, toggled off sharing all Messages, restarted the phone, and toggled it back on. In messages it said "syncing your messages" on the bottom for 15 minutes, so I was certain I'd found the solution... but still no.
Take 7) Checked this message board and tried switching the switching to multiple languages trick, multiple regions, starting/restarting. Nothing.
I've been at this for at least 4 hours (with the problem now going on for weeks), searching for answers and I can't think of (nor find) anything else. I paid a fucking $1000 for a new phone Apple! Am I supposed to guess when to pick up the phone? Memorize the number of every contact in my phone so I know who's texting or calling me? Just hope the numbers contacts randomly restore one magical day??
Seriously Apple, get this fixed!! I'm not even going to call support because I see that everyone here has tried it and they're going to tell me to do a full restart and re-download every last thing to my phone... not happening. (Also, your new Podcasts App format is abominable. I have no idea what's new, how many unplayed I have from any given one of the 55 pods I subscribe to, and there is clearly no way of fixing that either, because it's the phone default, not a user option.)
I have been an Apple enthusiast for over a dozen years and things just get worse with the increased amount of stream-lining every year. The MacBook Pro I bought in 2007 was the best one I owned (and still works!). I've upgraded two MacBook Pros since then, as well as two iPhones, an Apple Watch, and an iPad. Ever since the format of iTunes got wrecked to make Apple Music more seamless, things have been straight downhill.
Seriously Apple staff, figure this out. I'm tired of paying obscene amounts of money to have the "newest, best" version of an Apple product only to discover that the camera is 20x better and every other aspect (except memory I suppose) is worse than my previous iteration. I can't speak to everyone else agreeing with all of my anger about these various things, but at least fix the contacts issue! I don't answer calls from numbers I don't know... which is currently everyone. So essentially, I'm paying for the latest phone and a cellular plan so I can make calls and guess when it's worth receiving them. Ridiculous.