AMP Australia Post Shipping

I've loved the convenience of this app for a few years, but I think it may have become abandonware now :( I've been trying to get in contact with support regarding a change from Shopify that seems to have broken this app's shipping calculations for some addresses and not others, but they haven't replied. I'm hoping they see this and I can delete this review, but if they don't reply I'll be forced to switch apps as soon as practically possible.