So I was testing the invoice app but I see no way from the app to make the quantity of the item more than one other than to add the item again. Am 8 missing something?
Are you on the latest version of the app? Are you using Android or IOS?
I just tried it on my end (android) and everything seems to be working fine for me.
You could also try to clear the apps cache and or cache & data to see if that works.
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