@Player_1g1vsoqr Hi! Oh my! That sounds terribly frustrating. The only thing I can think of is that maybe the retail lot type isn't sticking. I've had some issues before with placing a lot on an existing build and the lot type not changing. May I suggest that you place the lot and then change the lot type to retail; you should get a prompt for this if there is a conflict between the existing lot type and the lot you're placing. Then save the game and exit. Then go back into the game (load game from save, not resume) and double check the lot type is retail for the lot you want your sims to buy. After they buy the lot, go into build mode and triple check the lot type is set to retail.
If that doesn't work, please consider sharing the lot you want to be retail to the Gallery so that we can test it. If you do this, name it something like "Retail Fail" so we know which lot to grab and hopefully other players will know there's a problem with it.
Seconding the possibility of the download's lot type not saving properly - I've had similar issues. I would place it from the gallery, check that it's set to retail, then save and exit. Then reopen the lot and check its lot type - is it still retail? If not, switch it again, save again, then try to purchase...
