How to make sure changes in Salesforce user records appear on Simpplr?

This has to be done by App Manager.

First, please make sure Simpplr is getting user profile information from Salesforce. Go to "Manage Application" > "People" > "User Syncing" page, select "Salesforce". 

Once you have selected the syncing source, you can select which fields to sync from the "Profile Fields" tab. The fields that are set to sync with your source will not be editable by users.

Go to "Setup" > "Schedulers", if you do not see a date under "Next Run" column next to "SchedulerUserDataSync", click on the drop down arrow and click on "Schedule".

If you are on Spring 18 or Summer 18 release, click "Schedule" next to "SchedulerSimpplrServices" instead.

Simpplr will synchronize the user data from Salesforce to Simpplr's People directory every night.