One distinct possibility is that there are no records that match the join conditions (esp. since you are using inner joins). One other potential issue is the View Designer doesn't handle joins of more than two tables very well. IMHO it seems to be constructing the SQL wrong. It should be like this:

SELECT Customers.company, Inventory_in.chgperkt, Inventory_in.clarity,;
Inventory_in.colors, Inventory_in.cut, Inventory_in.entered,;
Inventory_in.invoiced, Inventory_in.removed, Inventory_in.inactive,;
Inventory_in.karatwt, Inventory_in.measure, Inventory_in.p_descript,;
Inventory_in.stocknum, Inventory_in.total_chg, Transactn.track_num,;
Transactn.transdesc;
FROM inventory!inventory_in
INNER JOIN inventory!transactn;
ON Inventory_in.trans_id = Transactn.trans_id;
INNER JOIN inventory!customers ;
ON Customers.cust_id = Transactn.cust_id ;
GROUP BY Customers.company;
ORDER BY Inventory_in.stocknum

You might try firing that off in the command window and see what kind of results you get.