Hey @wendy10698,
When I click on the annotate tool from the left tool bar, my cursor changes to the pen icon, then when I write it is still a pen icon.
Are you using a pen and tablet? If so, check the preferences > Input > Tablet > Tablet API, try changing this to Automatic if it is not already, or try a different setting.
I’ve heard this can change some behaviours, it depends what tablet you have to what the setting is.
Also, do you have any add-ons installed? Other than Blender included add-ons.
They may also change the behaviour.
And finally, what version of Blender are you using?