Legal Removal Request

Post: Dear @ll, I have acquired 4 IO Pi Plus which will be distributed along my project to collect input. I have tested my setup by stacking the IO Pi Plus board directly ontop of the Raspberry Pi B 3+ and this works fine, input is detected. Then I separated the Pi and the IO Pi, isolated the "Link", connected +5V and GND to the external power supply port. I also connected a GND pin as well as SDA and SCL ports between Pi and IO Pi. This setup failed, i2cdetect found no device. Next setup: Pi and IO Pi are separated, no external power supply, re-established the 'Link", connected Pi and IO Pi by the following ports: 3/SDA, 4/+5V, 5/SCL, 6/GND. That also fails like above. Out of curiosity and because of the [url=https://www.abelectronics.co.uk/docs/pdf/schematic-iopiplus-2-1.pdf]schematic circuit diagram[/url] where an I2C Level Converter drains from +3.3V I tested the same setup, additionally connecting port 1/+3.3V - and this works, devices and input to them are detected. I could use an explanation of this behavior, because from the description you (I) get the impression that it would suffice to connect +5V and GND to the IO Pi Plus to the external supply port, merely connecting SDA and SCL with the Pi.When reading about connecting more than one IO Pi to the Raspberry on the documentations I found only the +5V and GND mentioned, no word about the +3.3V. If there is something missing in my setup please tell me about, I'm a programmer but no expert in electronics. Thank's a bunch, Walter