I get an ERR 99 message on my Canon Rebel Xsi

Hi. Take a look at the below link, it may be your solution.
Canon Rebel xsi Err 05

Err 99 could mean several different things, such as... Memory Card
Lens
Lens contacts....

A few things you can try.
Remove the memory card an enable "shooting with out memory card" and see if you still get the error. If it works your memory card is bad.
Try another lens if you can
Clean the lens contacts with a pencil eraser (be careful not to get eraser dust in the camera body or in the lens)
I have heard Canon recommend upgrading the camera's firmware (go to Canon's website to download the latest firmware and follow Canon's instructions for the upgrade).
I saved the worst for last, Err 99 could be related to the shutter failing which would mean a trip to Canon.
Good Luck

Welcome to Fixya
Err 99 could mean several different things, such as... Memory Card, Lens or Lens contacts....

Here's what you can try:
Remove the memory card an enable "shooting with out memory card" and see if you still get the error. If it works your memory card is bad. Try another lens if you can. Clean the lens contacts with a pencil eraser (be careful not to get eraser dust in the camera body or in the lens). Worst case scenario is, Err 99 could be related to the shutter failing which would mean a trip to Canon.
Thank you for choosing Fixya!

If you need further help, reach me via phone at https://www.6ya.com/expert/elixirjose_00375ea24bd8141b

Welcome to Fixya
Err 99 could mean several different things, such as... Memory Card, Lens or Lens contacts....

Here's what you can try:
Remove the memory card an enable "shooting with out memory card" and see if you still get the error. If it works your memory card is bad. Try another lens if you can. Clean the lens contacts with a pencil eraser (be careful not to get eraser dust in the camera body or in the lens). Worst case scenario is, Err 99 could be related to the shutter failing which would mean a trip to Canon.
Thank you !

If you need further help, reach me via phone at https://www.6ya.com/expert/elixirjose_00375ea24bd8141b

I can help you fix the BUSY Error or Error 99 of your Canon EOS Rebel XS / Canon EOS 1000D.

Installation of this Canon EOS Rebel XS / Canon EOS 1000D firmware version 1.06 update will solve these problems:

1. Some cameras may exhibit a phenomenon in which the LCD monitor does not display, the shutter does not release, and the BUSY indication remains lit in the viewfinder.
2. The message, "Err 99 Shooting is not possible. Turn the power switch to<OFF> and <ON> again or re-install the battery", appears on the camera's LCD monitor, and after the above operation is carried out,the LCD monitor displays in a language that is different from the actual language setting.

See the firmware instructions and download the firmware upgrade by following these Fixya Tips :

1. Follow this link to download a pdf version of the firmware installation instruction guide.
2. Follow this link to download the Windows Version of the Canon EOS Rebel XS / Canon EOS 1000D firmware version 1.06 update.
3. Follow this link to download the MAC version of the Canon EOS Rebel XS / Canon EOS 1000D firmware version 1.06 update.
4. Follow this link to download the Canon EOS Rebel XS / Canon EOS 1000D Instruction Manual.

I hope that helps.

If It's A canon Rebel, it has to go back to canon to be fixed, My girlfriend has one and the same thing happened to her's.

shutter struck, if the battery has no enough charge the shutter motor will not rotate fully,charge the battery and try.

err 99 is moisture or dew inside the camera.

Err 99 usually means your lens contacts are dirty either on the lens itself or on the camera.

To isolate the cause of the issue, do the following: -
1. Turn off the camera.
2. Remove the lens, battery, and CF card.
3. Allow the camera to sit without power for approximately 20 minutes.
4. Insert only a fully charged battery, and turn on the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, the camera may be faulty and requires a service. If it does not, then: -
1. Turn off the camera.
2. Insert the CF card.
3. Turn on the camera.
4. Format the CF card in the camera.
5. Depress the shutter button as you would to take a picture.

Does the “ERR 99" message appear? If so, then the CF card is faulty. Try a different card. If the message does not appear: -
1. Turn off the camera.
2. Clean the gold contacts on the lens by GENTLY rubbing them with a pencil eraser or soft cloth. Keeping the camera face pointing down, also clean the gold contacts on the camera, being careful that you do not let any debris fall into the camera body.
3. Reattach your lens.
4. Turn on the camera.
5. Depress the shutter button as you would to take a picture.

If the “ERR 99" message only appears when one particular lens is attached, then that lens should be examined by a service technician.
If you see the “ERR 99" with a different Canon lens attached, then the camera is faulty and should be serviced.

Error 99 is a "catch all" error that has several causes. It could be that your battery is not fully charged, especially if it is a generic, non-Canon battery. Charge for at least over night even if the charger says it's full. If that's not the cause, switches inside the camera will have to be cleaned by a repair shop.