Since you have changed the CMOS battery, it's likely that it might not be making a firm contact with the socket. Just try pulling it out and re-inserting it with bit more force.
If you are on Windows use app called HWiNFO and check what VBat voltage it reports?
Is it around 3.xx V or even lesser?
If you have a digital multimeter, then completely power down the PC, remove the power cord. Long press Power Switch on the PC case for 4 - 5 seconds. Now while the CMOS battery is in its socket, set DMM to DC Voltage, connect V+ to the top of battery and insert Grond wire to any free molex socket black wire pin. What Voltage does the DMM report?