problem changing the region in a DVD burner with Catalina 10.15 MacBook Air

Thank you for your kind reply. Both the generic and Apple DVD drives were brand new. As well as the computer. They ship with the region as number 1 ie. USA. In the UK they need to be changed to region 2. This would not occur despite the padlock being unlocked and the error message ‘not permitted’ appeared. The drive was taken back to the shop and they were not able to do it. They unboxed a brand new Apple DVD and were unable to change it as well. The same error message appeared. It states that one can change the region five times. We could not manage once. Then several hours were spent on the Apple help line, landing up with a very senior technician who also could not do it despite completely reloading Catalina. My other Mac could not do it either despite having changed two different DVD drives over the last year before Catalina was installed. It clearly seemed to be a Catalina problem. The region is held in an erasable reprogrammable Prom chip on the DVD drive and an old Windows XT computer sent the command effortlessly to it and changed it. This was my solution. It now works fine on the Macbook Air in the UK. I thought that this information might help others struggling trying to add an external DVD drive to their new computer or with Catalina OS.