OK, check for and clear out a clog in the piping.

Disconnect the sump pump from the discharge piping. There is likely to be a check valve, a fitting about the size of a softball, in the pipe somewhere above the sump. Take this out of the line and flush it out with a garden hose. Water should only run one way through it, observe the arrow.

While the check valve is out, stick a garden hose in the outside end, run water down the piping to clear out any debris.

Put the check valve back in, with the arrow pointing away from the sump.

Hook everything back up and cross your fingers.

If there is no clog, you will need to replace the sump pump.

Best Regards,
Jim