This doesn’t have to do with any technical issues, but rather it seems to have to do with the EU’s laws on privacy regulation which are currently being enforced. To ensure that Facebook complies with those rules, the company has limited certain aspects of both Messenger and Instagram while they sort it out.
However, for the most part the apps will continue to function. This means that you can still use both apps for messaging purposes, but certain features will temporarily be not available. This includes creating polls, giving nicknames to your contact list, and so on.
In a statement made to the BBC, Facebook said, “We’re still determining the best way to bring these features back. It takes time to rebuild products in a way that work seamlessly for people and also comply with new regulations.” It is unclear how long these limitations will be put into place, but it’s something that EU users will have to live with for now.