Because it's not like with the Bartenders. Generic Role Merchants (Food, Book, and General Store) have set hours that are not governed by the venue hours
which is from 9am to 6pm
<RoleType>GenericMerchant</RoleType>
<MotivesAdded>RoleLocationMerchant</MotivesAdded>
<StartTime>9</StartTime>
<EndTime>18</EndTime>

I have the mod that changes the generic role merchants hours of business. Regardless of that, its only 3 pm in the afternoon, all stores should be open, especially the merchant registers as EA sets them for practically 24 hours. It doesn't matter what time of day my sim goes to the store, the register always shows the store is closed even when the register is tended. I've also assigned one of my residents to tend the register.

I've shut the game down for the night, but maybe I should forget about my sim running the store and just let the game generate a role sim to tend the register. Maybe that would make a difference.

Yeah your right I looked at the wrong one. Not sure what is wrong unless assigning a home world resident could be the problem cause every time I've use those registers outside of the WA worlds I always had homeless sims get assigned even without Register.

I'm still preparing my world to play. Now that I've got it built the way I want it, I'm adding families and getting them all organised before I actually start playing. However, because I turned off allowing residents to be assigned role positions and stopped all role sims from being generated, I'm getting notices every five seconds about unfulfilled rolls, which is another thing that's driving me nuts LOL. Time to rethink what I'm doing... but not tonight

City Hall>Nraas>Register>Show Immigration Failure Notice
Whether to display a notice when the mod is unable to fill a role with any sim
Default: True <-----Change it to False
Hidden by: "Allow Immigration" = "True"

Thanks sittingbear, that's great info