How you enter pairs has changed. Change the _ to a - and it should work.
https://github.com/GuntharDeNiro/BTCT/wiki/Configuring-Gunbot#pairsPairs
In the pairs sections you can configure which pairs to use, on which exchange and which strategy should be used, optional overrides are possible. You need to remove any example pairs in the config.js file that you are not planning to use. Pairs need to be written in CAPS.
The set market coin is the one you want to accumulate. You use the base coin to buy another asset, and sell it back for profit in the base currency.
Gunbot normalizes pair notation, so all pairs for all exchanges follow the same logic:
BASECOIN-MARKETCOIN
All pairs with BTC as base currency are written like:
BTC-ETH, BTC-OK, BTC-XLM
All pairs with USDT as base currency are written like:
USDT-BTC, USDT-ETH, USDT-XMR