Thank you for the reply. 
I tried and run some tests on my side. Funny thing is if I used the old gst code of 7% it can get saved. But when I used the new gst code of 8% that’s when the error happened. 

I deleted and downloaded the app again from apple appstore, and tried to save using 7% and 8%. Nothing changed. Old code of 7% get saved but new code of 8% gets error code. 

I believe this is a system problem. I hope QBO can help to resolve this in the app.