Are you using mods? I know more mods which stop the use from umbrella complete or that the sim only uses a umbrella if it rains heavy.
As long your sim Is unplayed they get the standard umbrella in black. If you don’t like this, you need mods as Zero -> Season Umbrella Tweak (no random, your sim uses your picked umbrella) or LittleMsSam -> More Umbrella Variations in World (random umbrellas for NPC and inactive sims).
I used MC command enter to select the umbrella I made but it would not equip. Same with the umbrella stand
