Same thing: iOS 14/15 devices (ipads and iphone) cannot connect to marketplace. Images don't load and can't purchase minecoins. Everything else works normally. Tried multiple users and all of the devices we have. Same story.
Same problem here for the past week on iOS Bedrock edition. Tried uninstalling and re-installing, restoring system backup, restarting router, etc. Happening on multiple ipads and user accounts (me, my kids).
Been seeing "having trouble connecting to Marketplace, try again later" message. Can connect to online games. Cannot see any Marketplace images or purchase minecoins.
iOS 15, iPad and iPhone XS Max
Tried quitting/restarting – did not work
Tried resetting network settings – did not work
Verified local network access in Minecraft settings – still did not work
Deleted and reinstalled Minecraft – still did not work
Can access online games/realms, but nothing in Marketplace loads.