I have this same issue on iOS and macOS. If I haven’t visited the web site in several days, I often have to reset my settings (same ones David mentioned). Quite annoying.
The default layer is Wind. If you prefer Wind gusts, go to Settings > Start-up layer and location > Start-up layer > Use last overlay.
You need before to select Wind gusts layer with your preferred model of course.
@TrevMr12 Hello, if you would like to have Currents as your default layer, you can save it in Settings under Start-up location and layer. Just select Currents and choose "Use last overlay".
If it is about windy.com web site: retrieving always same map coverage, zoom level and even weather data layers, may be done by using API URL as a favorite in your web browser; see details here
@wowc87
With the app on IPad that does not works. You must log in on desktop to connect to Windy website and change the units on the color scale at bottom right corner of your screen. Then your setting is applied to your iPad app.