Running the brand new Spring 2019 release, and with the new Office 354 scanning, we're not seeing a full list of our users in 365. We have over a hundred, and LS is only picking up 57 of them. I've rescanned, I've checked credentials. No dice.
Take a look at the requirements article: https://www.lansweeper.com/knowledgebase/how-to-scan-office-365-accounts/
Make sure your powershell version and credentials have enough permissions. Otherwise it might be best to send an email to support so they can dig a bit deeper with debug options.