Please try to change branch id to 002 in "Settings" -> "General"
Why need change of code?
-> Because the ATO assigned a branch on the ABN. Possibly your client has two separate businesses under one ABN.
Failing that, check the following:
A. The ABN is still active.
B. The ABN is correct or That identifiers in LodgeiT are correct?
C. Can you able to lodge activity statement bas for other entities?
D. Can you confirm that this entity causing issue is in your ATO portal and has not expired?
E. What period does the BAS related to? ATO is not allowing lodgement for old forms, please lodge via portal.