And i’m not sure what is your hardware config, but You may need to set input pins as PULL_UP like this:
Thing mcp23017:mcp23017:chipA “MCP23017chipA” [address=20,bus=1] {
Type input_pin : input#B0 [pull_mode=“PULL_UP”]
Type input_pin : input#B1 [pull_mode=“PULL_UP”]
Type input_pin : input#B2 [pull_mode=“PULL_UP”]
Type input_pin : input#B3 [pull_mode=“PULL_UP”]
Type input_pin : input#B4 [pull_mode=“PULL_UP”]
Type input_pin : input#B5 [pull_mode=“PULL_UP”]
Type input_pin : input#B6 [pull_mode=“PULL_UP”]
}