How to change currency

Hello all,
I wanted to change the default currency from USD to ETB and i used
Setup-> Setting -> Global Setting
but while saving i get an error saying

Error: Document has been modified after you have opened it (2019-06-12 12:08:34.150491, 2019-06-12 12:08:34.150491). Please refresh to get the latest document.

and i refreshed it but still i get the same error message why is it?

As far as I know, you get this message when another document have been modified while you’re trying to change this one.
Generally, you just have to reload the page (clear-cache if you want to be sure) and it should work. I’m not sure why it won’t work this time…

I am still getting the same result. I even restarted the vm still no change.