To disable 2FA for a particular client, do the following:
Navigate to Clients > General.
From your clients list, select a client for whom you want to disable 2FA and click Edit client.
Click the drop-down menu icon (⋮ ▽) located in the upper-right corner of the screen, and then select 2FA from the menu.
Depending on which 2FA method is enabled for the client, select Disabled either in the google or sms drop-down list.
Click Save to apply the changes.