Try pressing Ctrl/Cmnd + \ to see if that brings back the top bar and repositions it in the monitor.
This looks to me like you are halfway between dual monitors. If that is the case try changing the display settings to mirror or unplugging the second monitor.
If all else, including a reboot, fails, try resetting your preferences.
A little more system info may be helpful in finding a solution.
this has happened to me before! try dragging the side of the window in while holding shift. it should also shrink the window vertically.
As Rick suggested, Maximize App Window ⌘+\ (command backslash) should work.
Maximize App Window on Primary Monitor ⌥+⌘+\ (option command backslash) should work as well.
If you decide to reset your preferences, hold ⌥+⇧+⌘ (option shift command) when you launch After Effects to be prompted by AE to delete your preferences file.
See if resetting the current Workspace/layout helps - Window>Workspace>Reset "current workspace name" to Saved Layout; where "current workspace name" denotes the name of the current Workspace.
Thank you so much! Originally this opened a zoom accessibility tool while simultaneously making after effects the right size- now I can use after effects. I want to thank everyone for all their replies. I was unable to respond as I was at work But I do thank all of you for helping me in this matter!