"survival entry-time is not allowed"

Hi,

I'm trying to estimate treatment effects in a dataset of unique individuals (approximately 3400 observations and 150 variables). I have a date under which they entered the risk pool, a date for when they left, and a failure indicator.

I keep getting the error "entry time expression <var> is defined; a survival entry-time is not allowed." after running stteffects. I am using Stata 14.1

I'm confused because I do not use the variable to stset the data (nor have I ever), but then if i explicitly set a different entry time, even if I streset or stset the data differently, I get the same error but with the different <var> that I had previously set to be the entry time.

My code is as follows:

stset time, failure(defacto_fail)

stteffects ipwra (agegrp sex comorbid region chemo_reg2 chemo_reg3 chemo_reg4 chemo_reg5 chemo_reg6 chemo_reg7 chemo_reg8) ///
(chemo_reg2 agegrp sex comorbid region chemo_reg3 chemo_reg4 chemo_reg5 chemo_reg6 chemo_reg7 chemo_reg8), atet

I've tried Googling the exact error message and searching the archives without any luck.

Many thanks for any help,
Marcelo