First, we need to check if IMAP is enabled. To verify this, click on the Settings > See all settings > Forwarding and POP/IMAP > Enable IMAP
Next, we need to check if less secure app access is toggled-on and if Klenty has third-party app access. To verify this, click on the Nine-dot Icon > Account > Security on the left-hand side.
Finally, check if 2-Factor Authentication is turned off. If it is turned on, you would need to set up an App Password, and enter that, instead of your actual password.