My router only has WEP encryption.

If using WEP you must complete the set-up using the PC method not the App method, this can be found here. This is because you must determine the level of encryption for security as the type of encryption determines the key length:

    A default key (also known as a pass phrase or network key) is selected for use on the network, and is usually located in brackets on the body of the Wireless router.

    64-bit hexadecimal keys are exactly 10 characters in length. (12345678FA is a valid string of 10 characters for 64-bit encryption.)

    128-bit hexadecimal keys are exactly 26 characters in length. (456FBCDF123400122225271730 is a valid string of 26 characters for 128-bit encryption.)

    64-bit ASCII keys are exactly 5 characters in length (DMODE is a valid string of 5 characters for 64-bit encryption.)

    128-bit ASCII keys are exactly 13 characters in length (2002HALOSWIN1 is a valid string of 13 characters for 128-bit encryption.)

Once you have determined the Security Mode, Key Type, Authentication and Key Index enter these as shown into the camera's Wireless Setup page under Network in the camera Settings area.

If in doubt about any of these details check with your ISP what these are.