try a reinstall,
either your config is corrupted or the addons list in the mission.sqm is missing something,
I have highlighted in red the possible mission.sqm addons that may be missing
class Mission
{
addOns[]=
{
"Trabant",
"Hunter",
"HMMWV",
"MM1",
"6g30",
"OH58",
"BMP2",
"BRDM",
"bis_resistance",
"bis_weaponpack",
"Bradley",
"AH64",
"Vulcan"
};
addOnsAuto[]=
{
"bis_resistance",
"Bradley",
"BMP2",
"BRDM",
"HMMWV",
"OH58"