If an issuer is not DTC eligible, then its shares cannot be...

If an issuer is not DTC eligible, then its shares cannot be transferred between brokerage accounts electronically, which basically means its shares cannot be traded easily. Major Exchanges such as NYSE and NASDAQ require DTC eligibility. Other Platforms such as the OTC Bulletin Board and the Pink Sheet markets do not. Only a DTC participant can request that DTC make a security eligible. Most large U.S. broker-dealers and banks are DTC participants. Once an issuer has been approved for trading by FINRA, they must apply to DTC for their initial eligibility to trade. If DTC approves the application they will hold all of the issuer’s free-trading street name shares on deposit. As with a Form 15C-211 submission to FINRA , an issuer cannot make a direct application to DTC for eligibility. The issuer must have a relationship with a broker-dealer or other financial institution that is a participant and will sponsor the eligibility process. This firm is also known as the “market-maker”. They will carry the initial position in inventory on behalf of their firm.
https://www.stctransfer.com/dtc-eligibility-information/