Possible Causes and Solutions :
A valve on a lateral line has is partially or completely open. Pig may have possibly entered side branch, or pig passed branch and product is flowing into it rather than pushing pig.
If flow is not being received at receiver, then pig possibly passed tee and did not try to enter. Ensure valves on all lateral lines are closed. Resume pigging operation. If flow is being received at receiver, then pig possibly tried to enter tee. If possible, try reversing flow from branch side of tee. Resume pigging operation. If unsuccessful, removal of the tee may be needed to extract pig.

The valve on the bypass line on the receiver is partially or completely closed.
Completely open valve on bypass line on the receiver.

Inadequate volume and pressure is being applied to pig.
Increase volume and pressure slowly, being sure to monitor pressure gauge for excessive pressure buildup.