The error CMN.ATO.AUTH.007 is ATO side validation. Please check this ATO guide and follow their instructions.
Also, try re-adding your authorisation for the client at the portal account level and see if this resolves the issue?
Please do as follows:
a. That the client is in your ATO Portal & you have permission to lodge on their behalf
b. That the ABN & TFN are recorded and matched correctly in LodgeiT 
c. That the ABN has not been cancelled. If it has, please remove it from LodgeiT.
d. Possibly there is a Branch Code. If so, attempt to replace 001 with 002 at Settings -> General.
e. If it's your first lodgement, check your Tax Agent details e.g. Tax/BAS agent number
In the instance of that, the error corresponds with CMN.ATO.AS.EM024, Access to the activity statement is not available. This may be due to:
To check that these details are correct, contact the Tax Office on 1300 139 373. You will need to supply the following information: name, address, TFN or ABN, account or client account number (if applicable), and the activity statement period"
There could be varied reasons of why the issue occurs. Usually in such cases ATO fixes the problem by re-issuing new Activity Statement.
If the issue still persists, User may contact ATO by phone directly and explain them the problem.