Synth command error: "R: operator invalid"

[Sounman Hong]

Hello all, I am trying to use synthetic control to identify the impact of an artist's sales strategy on the album's digital sales.
My STATA command is as follows;

tsset artistalbumcode release

synth lndigital lncdsales CV1 CV2 CV3, trunit(1) trperiod(14)

trunit = 1 is the treated unit (the artist), and trperiod is when the strategy was implemented (FYI, release variable ranges from 1 to 39.)
When I run the above commands, then I get the following error message during "the First Step: Data Setup."

'R: operator invalid'

Does anyone know about this error message?

[Richard Williams]

Did you get this from SSC? Can you get the examples from the help file to run? (You need to get the smoking.dta file to run the examples.) You want to make sure the program runs at all before trying to hunt down this error.

[Sounman Hong]

Dear Richard Williams, thank you for your willingness to help !
Yes, indeed, I tried the synth command using other datasets to see that it works nicely.
I have no idea why this command does not work with the current dataset. .....

Thank you again for your attention.