The Calc program is split into many component files; components are loaded automatically as you use various commands that require them. Occasionally Calc may lose track of when a certain component is necessary; typically this means you will type a command and it won't work because some function you've never heard of was undefined.
If this happens, the easiest workaround is to type C-x * L
calc-load-everything) to force all the parts of Calc to be
loaded right away. This will cause Emacs to take up a lot more
memory than it would otherwise, but it's guaranteed to fix the problem.