Hello,
Which version of CodeWarrior are you using?
Does the Clean build that you tried is by using the commander>Clean (All)?
When you move to a new project it works and after a few weeks happens again?
Probably your make files doesn’t match according to your directory.
Please try this to clean and make a re-creation of the make files
On the Project view>Clean>Select your project to build
luis_maravilla_1-1787091476012.png
Also, as a recommendation do not use the Dropbox folder, kindly change to a local path and add it or change it in the build directory.
Please refer to this post for more information No rule to make target | MCU on Eclipse
Best Regards, Luis