I use the MoonBot terminal to trade on the spot using Telegram signals and I sometimes buy on a USDT-T coin without a signal on it, what could be the matter?

: Interface configuration

If you use the MoonBot terminal to trade on the spot using Telegram signals, make sure that the Special check mark is unchecked on the Settings – AutoBuy tab, otherwise, as in your case, the terminal may mistakenly identify the USDT-T market in the signal.