This error message could be due to a few things
Make sure your iOS device is up to date with the latest iOS firmware i.e. iOS15
Try powering off the Wi-Fi speaker via the mains to clear any cached memory. Restart the speaker, and add it back to the network to see if this fixes the issue.
The communication signal from the Wi-Fi signal may be low, we suggest setting up and placing the router in the same room as the Wi-Fi speaker to test and the router now placed in the same room to see if it can pick up the connection.
Please note: it may take a couple attempts to connection before it takes affect and pairs.