Picture and group messages (MMS) are downloaded through your mobile network, not Wi-Fi. "Multimedia message couldn’t be downloaded." usually means the phone couldn't reach the network's MMS service.
What to try:
- Turn on mobile data, even if you're on Wi-Fi, then tap the message to try again.
- Check that you have signal and that airplane mode is off.
- On a dual-SIM phone, mobile data must be on for the SIM the message came to.
- If MMS never works, your SIM's MMS settings (APN) may be missing: your network can send them, or they're in Settings → Network → Mobile network → Access point names.
Some networks also need MMS to be part of your plan. If it still fails in 1krBlocker but works in another SMS app, contact support.