Struggling to join friends worlds on bedrock edition

Every time I try joining my friend's world through invite, it loads a loading box with no bar and only the cancel button. This goes on for an endless period of time until it finally times out and I get the kelp error code. This also occurs to them, and it's been this way for days. Her world doesn't appear on my screen, and neither does hers. We are both logged in to Microsoft accounts and have updated our games. One day, this issue disappeared, but reappeared the next day. How can we fix this?