after spending some time trying to get into advanced mode on my second iogear KVM, I finally figured out what's wrong. on the user manual it says:

1. press and hold clear key for two seconds.

2. press and hold minus key [-] key for one second.

3. release minus key [-] and within one second also release clear key

when, in reality it should be:

1. press and hold clear key for two seconds.

2. tap on the minus key.

3. release clear key shortly after.