When PS changes fonts, some fonts cannot be changed. What happened?

Text that has been rasterized or converted into a layer cannot change its font, and other fonts can be changed. Specific operation reference is as follows:

1. First, open the photoshop software.

2. After opening, press CTRL+N to create a new canvas.

3. After building the canvas, click the text icon in the toolbar.

4. For example, the font of the input text [New Knowledge] is relatively small and needs to be enlarged, so please click the font size in the character toolbar on the right, as shown in the figure.

5. Select 72 fonts from the drop-down menu.

6. If it is not big enough, click the font size box.

7. Finally, manually enter the required font size, such as 200, to make the font bigger.