Canadian stocks have their own ticker symbols, they are separate from the U.S tickers.
Radient is a Canadian company so the primary ticker is RTI not RDDTF.
RTI is the canadian ticker
RDDTF is the U.S ticker
They are both Radient Technologies
If the U.S side is closed and the Canadian side is open you will see RTI trading and RDDTF will not and vice versa. Yesterday was not the true norm as there were no trades on the U.S side for RDDTF even though the market in the U.S was open.