Its this display (sorry it is in Czech language but datasheet and code is clear I hope)
https://arduino-shop.cz/docs/produkty/0/114/1487765029.pdf
https://navody.arduino-shop.cz/navody-k-produktum/oled-displej-ssd1306.html
I tried 2IC on Arduino Mega and it works well.
I tried SPI Oled (7 pins) on Teensy with U8glib.h library and it works.
I tried 2IC on Teensy with U8glib.h (SSD1306) and it is problem.
Assuming you have the correct pinout for I2C (pin 18 for SDA, pin 19 for SCL), ground, and VCC/3.3v, there are two common issues you might be running into:
The first issue is I2C buses on the Teensy need 2 pull-up resistors (one between SDA and 3.3v and the other between SCL and 3.3v). Older AVR processors like the Mega did not need pull-up resistors, but ARM processors like the Teensy or the newer Arduino platforms need pull-up resistors. Many newer devices include pull-up resistors in the device, but not all devices do, especially the older devices. Note, if you have multiple devices on an I2C, each with a pull-up resistor, the combined resistance may mean you can't use the fastest I2C modes (but you should be able to use the slower standard mode).
A pull-up resistor is a resistor that is wired in parallel to the data. I.e. one end of the resistor is connected to the data pin (18 or 19 in this case) and the other to normal voltage (3.3v). The data connection is also connected to the pin. For 3.3v systems like Teensy, a common value for the resistor is 2.2K ohms. For 5.0v systems, 4.7K is a common resistor value. Teensys will work with 4.7K resistors.
The way to see if you need pull-up resistors is to run the Examples -> Wire -> I2C scanner with the device connected. If you see the OLED monitor in the list of devices connected, than it means you don't need pull-up resistors. If the scanner hangs or has errors, you will may need to add pull-up resistors (or check your wiring).
The other issue is voltage. Some displays need 5v to run, some are happy with 3.3v or 5v. If you are mixing voltages (5v for VCC, 3.3v signals for SCL/SDA), you may or may not run into issues. Most new devices will automatically convert the SDA/SCL output to 3.3v so it is safe to use on 3.3v devices. Older devices might use the 5v power on the I2C bus. With the exception of the Teensy 3.1/3.2 and 3.5, all of the ARM Teensys might be destroyed if they receive 5v input signals. If you have a mixed voltage I2C bus setup,you may need to use bi-directional voltage level shifters.
So the simplest pinout is to try 3.3v connected to VDD, instead of VIN. That way the I2C bus is all 3.3v.
I have run into older displays as I moved from an Arduino Uno to Teensy where the display needed 5v to be able to display anything. If you used 3.3v and hooked up the scanner sketch, it would show the device being on the I2C bus, but you wouldn't be able to see anything until the display was fed 5v.
Depending on the device, where you are located, your budget, etc. sometimes it is simpler to get a new device that works with 3.3v directly and has pull-up resistors then to do the trouble-shooting.
One other thing about voltage -- the 3.3v pins can deliver roughly 250mA of power. The Teensy 4.x generally uses 100mA of power. In theory, you should have enough power for 1 display, but if you hook up multiple displays, you might find the displays consume too much power.
Good luck.