You are welcome. I'm glad it is working again now.
I mentioned in my reply how the Serial Monitor component of Arduino IDE 2.x is only a GUI for displaying data received from the helper tool, and for passing data input by the user to the tool.
This separation of the low level capabilities into a separate tool was done intentionally in order to support a "pluggable monitor" system, where platform developers can create their own custom tools to handle any imaginable type of communication between the computer and the Arduino board. This means that the "Serial Monitor" name of the Arduino IDE component is greatly underselling the feature since this can now be used for any type of communications; not communication over a serial port alone.
A big part of the motivation behind the creation of this system was that creator of the Teensy boards, Paul Stoffregen had found the Arduino IDE 1.x Serial Monitor to not meet their requirements and wrote a replacement. This was one of the things that made it necessary for Paul to maintain a modified version of the open source Arduino IDE 1.x ("Teensyduino") in order to provide Arduino framework support to users of the Teensy boards. One of the design goals for the Arduino IDE 2.x project was to make the tool flexible and powerful enough that it could accommodate the emerging requirements of the ever expanding ecosystem of Arduino boards, both for Arduino's own official boards as well as the huge number of 3rd party boards such as the Teensy line.
So Paul Stoffregen actually wrote their own monitor tool (which is called teensy-monitor) for Arduino IDE 2.x and that tool is used by the Arduino IDE 2.x Serial Monitor when you have selected the "Teensy" protocol ports used by Teensy boards. This is the reason why the "Port monitor error: EOF" error will only occur when Serial Monitor is used with a "Serial" protocol port, which causes the now Windows 7 incompatible serial-monitor tool to be used.