On this forum there are a number of topics where someone has a working I2C bus, which does no longer work when adding a OLED display. It seems to happen mainly when a OLED is connected to a 5V I2C bus.
The OLED displays are sold as 3-5V, but that is not true. They are internally 3.3V, so they have a 3.3V I2C bus.
In the past some OLED displays did not even acknowledge to their address. I hope those are not sold anymore.
Adafruit puts a level shifter between the I2C bus and the OLED (see schematic), that is the right thing to do. But then Adafruit uses the Stemma QT bus, which is wrong because SDA is next to SCL.
I can go on for days with this, but I already wrote some things in a Github wiki.