TOTP on Netextender Causing Authentication errors

I'm working on an issue with the NetExtender, with TOTP enabled LDAP users are getting this error 'Authentiating...failed!'. When I turn TOTP off, no problems whatsoever. We need this to be on as they had recently had a large amount of 3rd parties trying to access their systems. Is there any way to resolve this? Just for info they are on a TZ270 and it's on the latests firmware (SonicOS 7.1.1-7051).

Edit: for some reason this does not affect local accounts only LDAP ones.