Not able to add css file to download on page

I am trying to add a custom css to my custom page,

I added the following code to

app_include_js = [
app_include_css = [
web_include_js = [
web_include_css = [

The fpo,min.js file is getting picked up fine, but fpo.css is not getting picked up.

Is there a known issue?
I see that erpnext.css is getting picked up. It is part of erpnext\

app_include_js = "assets/js/erpnext.min.js"
app_include_css = "assets/css/erpnext.css"

So no success when you try these -

Reload (menu item dropdown when you click Userid, next to Help)

bench clear-cache
bench clear-website-cache

Try Chrome & Firefox and clear browser cache…

Thanks clarkej
bench-clear-cache/bench clear-website-cache worked.