That tells me your brakes need fluid to be added, yes and burped to get the air out.

Putting the bike upside down for few hours won't resolve the issue. It needs more mineral oil.

Also, you don't really need a full bleed kit. An $8 funnel and mineral oil would suffice.

https://www.amazon.com/RSN-Sports-St...s%2C122&sr=8-3