I fit the full multinomial logit model for all four alternatives of my response variable and four restricted multinomial models in which one alternative is excluded:

estimates dir

---------------------------------------------------------------------------------------
name | command depvar npar title
-------------+-------------------------------------------------------------------------
m1 | mlogit IntlFW 280 all four
m2 | mlogit IntlFW 280 IntlFW != No Intl FW :IntlFW
m3 | mlogit IntlFW 280 IntlFW != AA1000 only :IntlFW
m4 | mlogit IntlFW 280 IntlFW != ISAE3000 only :IntlFW
m5 | mlogit IntlFW 280 IntlFW != Both AA1000 & ISAE3000 :IntlFW
---------------------------------------------------------------------------------------


I then increased the matsize to 800 (I have Stata IC) and the used the following code to conduct the suest test:

suest m1 m2, vce(cluster CompanyName) noomitted

However, I am getting the following warning and an empty results table: "Warning: variance matrix is nonsymmetric or highly singular"

I also used dataex to include some of my data with this question, but I Stata is giving me the following response:
dataex IntlFW i.NumTypeofAP GeoRevSeg ROA LMarketCap DisclosureIndex MandatedAssurance i.FSaud
> itorCode i.SVCGrouped i.NumHQ i.Fiscalyear, count(150)
factor variables and time-series operators not allowed
r(101);

Do you know what the warning in red above means and what I can do to get a proper response for my suest test? I would be very grateful for some help.