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.