The error message "invalid S/L or T/P" may occur for the following reasons:

Incorrect placement:
The stop loss (S/L) or take profit (T/P) level is set too close to the current market price, violating the platform’s minimum distance requirements.

Wrong side:
The stop loss or take profit is placed incorrectly relative to the order type:

• For a buy order, the stop loss should be placed below the current market price and the take profit should be above it.
• For a sell order, the stop loss should be placed above the current market price and the take profit should be below it.