Question about the use of the CAS solve function in a program

[StephenG1CMZ]

Yes.

To use a cas function from a home program, you generally need to identify it as a cas function to distinguish it from any similarly-named home function.
So instead of:
fun(...)
try:
cas.fun(...) or
cas("fun(...)")

Or, perhaps the tips in this thread may help:
https://www.hpmuseum.org/forum/thread-17051.html (solve problems)
- Douggg suggests Solve.SOLVE [using the Solve app, not CAS], and others have the expression in quotes.

[updated to add link to thread]