Why wont the recent update on iwatch install

What happens when you try? Any error messages, etc.? What series watch? What watchOS version is currently on it? What model iPhone? What iOS version is on it? Without knowing anything else, perhaps one of these articles will help:

If you don’t have enough space to update your Apple Watch - Apple Support

If you see 'Unable to Verify Update' when updating Apple Watch - Apple Support

If the update fails, see fireyjack's reply to:

apple watch 3 series won't update , w… - Apple Community

I was given a 7000 series Apple Watch - Apple Community

What series of Apple Watch do you have? See this about updating the Apple Watch. Update your Apple Watch - Apple Support

Nothing happens. Absolutely nothing. There’s a quick spin and it looks like you never tried. I’m now trying to install the update from the watch itself. At least it was downloading there.

And the instructions for deleting the download manually are wrong. There is no “Usage” setting under “General”.

Same thing is happening to me. Just spins forever and ever. Downloaded, but won’t install. After the 15.3 OS download.