It would be helpful if the version of Sitecore/EXM were listed in the question, as this could be a result of many different issues. However, based on the information provided, I am led to believe that the user is operating on Sitecore 9.0.1 EXM. If this is the case, there is a known issue with personalization.
Referencing the Cumulative hotfix for EXM 9.0 Update-1 from Sitecore, this hotfix includes a number of fixes for issues found in 9.0.1 EXM. Of these issues, is the Analytics Personalization, which wasn't being applied to the message body. In short, the personalization you are attempting to use requires the use of the Analytics Tracker which is unavailable OOTB with Sitecore 9.0.1 EXM.
Installing this hotfix (or upgrading to Sitecore 9.0.2) fixes this issue. Other issues fixed listed in this hotfix include:
- Segmented Lists are not considered as a contact data source during the dispatch process.
- Attachments cannot be removed from a message.
- The Click Email Link goal usage can lead to an exception in log files.
- The number of Sent metrics in the message statistics is wrong.
- Message statistics are not updated properly because of caching.
- Analytics personalization may not be applied to the message body.
- NullReferenceException may be thrown if Email facet is empty.
- Dispatch may be paused if used lists contain PII sensitive data.