When "Use active symbol and exchange" is checked (it is by default), make sure you're looking at an exchange that publishes both longs and shorts data on TV.
For example, if you're looking at BITFINEX:BTCUSD, this script will display BITFINEX:BTCUSDLONGS and BITFINEX:BTCUSDSHORTS (note the automatic suffixes).
When unchecking the "active symbol" box, you have to put the full symbol for longs and shorts in the corresponding fields.
For example, when looking at BITMEX:XBTUSD, uncheck "Use active symbol and exchange" and manually put "BITFINEX:BTCUSDLONGS" and "BITFINEX:BTCUSDSHORTS" in the respective suffix/symbol fields.
For example, if you're looking at BITFINEX:BTCUSD, this script will display BITFINEX:BTCUSDLONGS and BITFINEX:BTCUSDSHORTS (note the automatic suffixes).
When unchecking the "active symbol" box, you have to put the full symbol for longs and shorts in the corresponding fields.
For example, when looking at BITMEX:XBTUSD, uncheck "Use active symbol and exchange" and manually put "BITFINEX:BTCUSDLONGS" and "BITFINEX:BTCUSDSHORTS" in the respective suffix/symbol fields.