If you turned this into static SQL, did you replace single quote correctly? There is an extra END after RevCnt which should be removed, e.g.

Select e.Category, e.EnteredBy, 
rtrim(u.UserLastName) + ','  +  u.UserFirstName as FullName, 
COUNT(  case when r.checkid =0 then 1 end)  as chkcnt, -- comma here
COUNT(case when r.CheckId= -1 then 1 end) as revcnt

FROM ExpMaster as e
INNER JOIN ReviewHistory as r
ON  r.XPID = e.origid
INNER JOIN UserFile as u
ON u.UserInit = e.EnteredBy
WHERE e.EnteredBy = 'DAB' and e.EnteredDate between @mbDate and @mbEDate
group by e.Category, e.EnteredBy, u.UserLastName, u.UserFirstName
order by e.EnteredBy

If you want to keep this dynamic, then use sp_executeSQL and parameters as is, take a look at this blog
Avoid Conversions In Execution Plans By Using sp_executesql Instead of Exec