Citrix Director shows License server issues as follows:
License server state: OK
Grace state: In Supplemental Grace Period Time until grace expires: 6 days 4 hours License server status is "Not Connected".

Studio is able to connect to the license server, there are enough licenses and license server is showing that licenses are being used as expected. 

According to the Citrix Documentation: https://docs.citrix.com/en-us/licensing/current-release/license-types.html#supplemental-grace-period

If all licenses are in use, including the license overdraft where applicable, the supplemental grace period gives you time to determine why you exceeded the maximum license count and to purchase more licenses without disrupting your users.

After the supplemental grace period expires, normal connection limits are enforced. Users are not disconnected during active sessions. As they disconnect, however, no new connections can occur until the license levels return to normal.

The supplemental grace period is not automatically re-enabled once it completes. To re-enable the supplemental grace period, you must install another retail license. This retail license grants a new 15-day supplemental grace period if and when you exceed the subsequent maximum installed license limit.

We recommend that you allow the supplemental grace period to run out after it starts. To clear the warning condition do not add licenses immediately. Doing so gives you time to fully assess the situation and correctly address any issues." 

So this behavior is normal and the only way to turn this off would be to follow -
1) Go To:C:\Program Files (x86)\Citrix\Licensing\MyFiles\
2) Open the file: "CITRIX.opt" with Notepad.
3) At the bottom of that file, add
"#CITRIX SGPOFF"
4) Save
5) Restart all Citrix Services (or Reboot)

to remove supplemental all together or to add new license files.

It is worth noting that the Supplemental Grace Period is normal when a user goes over the allotted number of Citrix license.

It is also normal for the error to show up in Director even after no SGP licenses are being used.

The SGP is a one time grace period that last 15 days. After this there can be no more SGP licenses applied to uses but normal ICA licensing will occur.

The idea is that you have 15 days to correct the issue before the SGP and only the SGP licenses expire. There are 2 options:  apply existing unallocated licenses or purchase additional licenses.

https://docs.citrix.com/en-us/licensing/current-release/licensing-technical-overview.html