I wasn't aware you could buy OTC equities from Robinhood.
Even their help center states you can't.
You can trade over 5,000 securities on Robinhood, including most U.S. equities and exchange trade funds (ETFs) listed on major U.S. exchanges.
We do not yet support the following, but hope to in the future:
•Foreign domiciled securities*
•OTC equities
•Options
•Preferred Stocks
•Tracking Stocks
•Warrants
•Mutual Funds
•Bonds and fixed income trading
•Foreign Exchange
Can you trade OTC?