Most of stock trading occurs on what is called a secondary market. For example, Microsoft is traded on NASDAQ, which is a stock exchange. An analogy that can be made is that of selling a used car. When you sell a used car to a third person, the maker of your car is unaffected by this transaction and the same goes for stock trading.
Still within the same analogy, when the car is first sold, money goes directly to the maker (actually more complicated than that but good enough for our purposes). In the case of stock trading, this is called an Initial Public Offering (IPO) / Seasoned Public Offering (SPO), for most purposes.
What this means is that a drop of value on a secondary market does not directly affect earning potential.
Let me add some nuance to this. Say this drop from 20$ to 10$ is permanent and this company needs to finance itself through equity (stock) in the future. It is likely that it would not be able to obtain as much financing in this matter and would either 1) have to rely more on debt and raise its cost of capital or 2) obtain less financing overall. This could potentially affect earnings through less cash available from financing.
One last note: in any case, financing does not affect earnings except through cost of capital (i.e. interest paid) because it is neither revenue nor expense. Financing obtained from debt increases assets (cash) and liabilities (debt) and financing obtained from stock issuance increases assets (cash) and shareholder equity.