Apple Watch can't connect to apple fitness

This question was asked previously but I am having this exact same problem and can't seem to get clear guidance on what to do.

Im connected to the same wifi network each time. Ive tried disconnecting from the wifi and using cellular data and that also does not work. This is my 2nd iPhone 15. My original one got sent back because it would not charge properly. With my first one I did not have any issues.

when I work out with my apple watch I can't get the watch to connect to the fitness app workouts. For example, I will find a workout I want to do but when I click on it it says 'Looking for apple watch' (my apple watch and phone are connected fine with all other things). It will look for my watch to connect for a while and then says 'unable to connect to apple watch.'

I have tried everything to fix it including, restarting my phone and watch, clearing all the data and starting from the beginning, updating my phone and watch etc

I receive messages/app notifications on my watch so do not have any issues with the connection usually.

If anyone can help that would be great!