Hi,
We have come across a bug in Directadmin update v.1.670 and that is the cause of the issue :
https://docs.directadmin.com/changelog/version-1.670.html
To confirm this we had a Directadmin test server with v.1.669 and we were not able to replicate the issue you mentioned. As soon as we upgraded to v.1.670 we faced the same issue on our test servers.
This issue is happening because in the new version Directadmin API is not validating the session correctly and hence returning empty response on all API calls made by Softaculous to Directadmin API.
Note: This is happening only when you login to Directadmin panel as "admin" or "reseller" and then switch to another user account and then access Softaculous.
If you login as the user directly in Directadmin panel and access Softaculous it works fine.
Until this issue is fixed by Directadmin team you can use the workaround to access Softaculous as a user instead of logging in admin/reseller and then switch user.
Below is an extract of the log we found from Directadmin logs :
Authentication::creatorValid: got type 3 for user admin
Authentication::creatorValid: failed: Password () is not valid for 'admin', so cannot login as 'user1'
We have emailed the Directadmin team regarding this issue and once we get a response from them we will update you.