Bedrock realms refuse to load if I use Marketplace addons

I am having this issue also, on Windows 10 and X-Box, worlds with marketplace world templates are not loading (they load fine locally), but worlds without load fine. I have tried Stoneblock 3 by FTB and Custom Hearts by Glowfischdesigns. For me this doesn't seem to be an issue with regular marketplace add-ons, just the templates.

I've been having the same issue, my world with RealismCraft, Naturalist, and FURNITURE (XP games) has not been working. I've tried playing mobile and on Windows 10. Additionally, my realms bugged out and my main world got overwritten by a duplicate copy of the Realms Celebration map and it's stopped letting me replace my worlds whatsoever showing me a "failed to find place to upload world" notification. I don't know if the worlds bugging is a separate issue but they seem aligned enough that I'll add it to my comment.

Ok, looks like we're on the right track looking at the previous comments. Thank god I'm not the only one. Spent way too much money on these addons just to realize they don't work on Realms. 🗿 Hiyaa.

I have the same exact issue. Problem only began happening for me after the latest Minecraft Patch (1.21.2).

I can use a Realm with experimental addons installed.

I can use a Realm with no addons installed.

I can NOT use a Realm with any Marketplace addons or worlds installed.

The addons only work on non-payed worlds (Not Realms).

This issue is happening for me when I use Realism Craft or The 15th Anniversary world. I also have several other addons (not worlds) like Naturalist, Natural Disasters, etc.

I’m having this exact problem too. I’m trying to play on a marketplace map, Adventures and Dungeons, and I’ve tried using multiple different combinations of add-ons. Warpstones add on by mythicus studios, utilities by teplight, air drop by bunny studios, double jump boots add-on by blocklab studios, trims add-on by blocky, mushroom pets rp add on by captainsparklez, and tinkers construct add on by FTB. I tried them in multiple different ways and even one at a time, but it never worked. So frustrating 

Hello! We are actively investigating this issue. We believe it is an issue with one of our services and so will not require another client hotfix to fix this specifically. Thank you for the great information shared in this bug. I will update here when the issue is resolved. 

I have the same error on all devices!

A fix for this is rolling out now. It may take a little while for the fix to sync globally across all Realms servers. Please let us know if the issue persists after a few hours. 

I'm having the same issue with my realm since yesterday! On Windows 11 and all the members inside the realm. I have add-ons like RealismCraft, Security Add-On, Security++, SparkPets Premium, Naturalist, Essentials, etc. The loading bar gets stuck approximately at 1/3.

Realms now don't recognize world add-ons, they don't work, and they don't even appear in the world settings section.

IT IS WORKING!!!
Thank you for looking into this issue! ^^

From the tests I did, the RealismCraft add-on is the only one that does not work, like in a new world and in one already created

Things seem to be working for me now. Thanks for the quick turn-around.

Great now I can get on realms, but realism craft is completely broken on realms.

The issue of Realms not allowing players to join/play with template worlds such as Realismcraft is fixed. If you are having issues with the pack not applying properly, but still being able to play on the Realm, please try downloading the world, resetting the slot, and then reuploading the world after you have verified the packs are working properly locally. If the issue persists, please file a separate bug. If you are still unable to join your Realm though, please reach out to support so that you can provide gamertag and Realm name for us to investigate further. 

More Custom Blocks Add-On by MrAniman2

More Blocks by RareLoot

Another Furniture Add-On by Starfish Studios

some of these add-ons also say that some content can’t be added and rhats’s where the problems seem to start. Then no one can get into the realm.

We are looking into further reports of broken Marketplace Addons

As far as DLon King recommended "try downloading the world, resetting slot, and then reuploading the world".....  I would love to, however the inability to download worlds over 1.4Gb still has Not been fixed.  After years of waiting, the realm myself and all of my friends have been playing on, we still cannot download a copy of the world or even manually download a backup.  Pretty sure this issue has existed since like 2017