This wouldnt be the first time chorus has upgraded dslams and suddenly made telepermitted modems incompatible.
At a previous job, we were replacing modems around hawkes bay non-stop for a few days when they decided to upgrade some firmware in the dslams and a whole bunch of spark modems were no longer compatible.
Was unfortunately the customers who had to argue our bill with spark, and spark probably couldnt get a refund from chorus.