Please check that Expand abbreviations is checked in TextExpander’s Expansionpreferences.
Please click the TextExpander menu bar item and ensure that the second item reads Disable Expansion rather than Enable Expansion. If it reads Enable Expansion, please choose Enable Expansion:
If the TextExpander menu bar item notes something about secure input, please review this.
If none of that helps, please see if you able to expand snippets by choosing them from the TextExpander menu bar and contact support with the details.