romance bar is not showing up

This might be an old thread but I had the same issue and managed to fix it. Basically, my game was corrupted in some way, it was probably due to a Mod ( that I've deleted long ago, but a folder was created in my saves file). What I did to fix it was,

1. make sure the game is not running, exit it if so.

2. Copy and paste my save file, tray file and Mod file somewhere safe (computer or hard drive),

3. Delete the Sims 4 Folder in Documents > Electronic Arts > The Sims 4 (I play on Mac so check where to find this file on whichever platform you play).

4. I started running the Game fresh, don't worry it will create a new Sims 4 file in your EA folder, brand new. 

5. I created a quick new game and tested out with two sims, make sure they're not partner, fiance or married.

6. Once your new game is set up, use the cheat code to increase and decrease the friendship relationship between these two :

Shift + Control + C > testing cheats true > ModifyRelationship Sim1FirstName Sim1LastName Sim2FirstName Sim2LastName -100 LTR_Friendship_Main

This should modify their friendship bar as a test so you know your code line is right, now try it with the romance cheat :

ModifyRelationship Sim1FirstName Sim1LastName Sim2FirstName Sim2LastName 100 LTR_Romance_Main

If you see the Romance Bar filling up, then it means your fresh new game is fixed and it was either a mod or a corrupted file that was causing the issue

7. Exit your game and copy and paste your save files in Folder in Documents > Electronic Arts > The Sims 4 > saves, make sure to only put files started with "Slot_" and nothing else, 

8. Run a test without adding your Mods and Tray files, with the same cheats as step 6. 

If it works, congrats you fixed your game, now you can start adding your Mods and Tray files carefully, for me it worked but if a certain Mod is at cause, then you should repeat the step 6 as much as you can while removing and adding Mods until your game is fixed. 

I know it is a tedious work but for my gameplay I had to fix this as I am playing Fiona and Shrek with a enemy to lover storyline lmaaoo. Couldn't pass on this, but I am glad it's fixed. Hope it helps.