At last! I have been waiting for two deliveries from Australia for a few weeks, wondering if they had got lost in the post. They have now arrived. The first set was the Sports Stadiums issue from March: 4 stamps with normal gum and 4 self-adhesive. The April issue, with the same quantities, was to commemorate Anzac Day. This second issue also comes with a mini sheet.
On reflection, it is easy to see what happened. Due to the virus, there are very few flights into or out of Australia. So all mail to foreign destinations is delayed. You might be lucky with your letter but others have been delayed by weeks. I am finding the same with Canada, where my supplier sent me more material some time ago, but no sign of it as yet. This virus ha definitely affected all aspects of our lives.