If you think you have installed the Lot Management tool correctly on all of your GP user machines but lot allocations are not showing up in a certain users GP you may want to check the install to confirm.

To do so please open windows file explorer and make sure the LotMgmnt.dic file exists in the users GP directory. By default installed in C:\Program Files (x86)\Microsoft Dynamics\GP\

As the image above shows there is an allocation on this item of 1040 BUT when the user opens the allocation window to see the details nothing shows up.  

The reason the window is not showing anything is because GP has triggers that add allocation records to this window for different GP modules as well as ISV products.   If this trigger does not exist (because lot management install was missed) then the Item Allocation Inquiry window will not show the allocations properly.

After installing Lot Management into the GP instance the allocation correctly appeared.