Some bike power pedals are able to measure the left and right side power. They also transmit the power using two different Bluetooth connections. However, to use those pedals with the Selfloops Spark app you need to link those signals so they will transmit their data over a single Bluetooth connection.
If you have Stages pedals, you can use the Stages app to “link” the two sides.
If you have the Favero Assioma pedals you can link them using the Favero app and choosing the Unified Channel L option.