The projects sample rate cannot change, unless you export each track individually and then re-import it into a project that has a different Sample Rate.
SOOOOO, this means that your sound card's sample rate has changed, not your SonofBandlabCake project
 
TO SOLVE, change your sound cards sample rate to the projects sample rate

This is true only if there is audio in the project. The sample rate is not fixed if the project is all MIDI. All MIDI projects use the sample rate in Preferences. Changing the sample rate in preferences effectively changes the sample rate for all MIDI only projects.

vERY tRUE

Close cakewalk, then open the Focusrite mix control. Set it to the sample rate you want. Then reopen cakewalk, open the project and set the sample rate to the rate you previously set in Focusrite. I had constant problems with this until I hit on the trick of always opening the Focusrite mix control first.