Don’t have permissions to run sp_updatestats

The user must be the database owner (not just in the db_owner group) or be a member of the sysadmin server role to run sp_updatestats.

Another option is to create a stored procedure using the “execute as” clause and assign execute permission to the user that needs to update statistics:

create procedure dbo.sp_updstats
with execute as 'dbo'
as
exec sp_updatestats
go  

grant execute on dbo.sp_updstats to [<user>]
go

Where <user> is the user you are assigning permission to run this new stored procedure.