You may need to follow the procedure explained below:
Step 1 Set the static IP address of the PC on which your TFTP server software runs to an address between 10.0.0.2 and 10.0.0.30.
Step 2 Make sure that the PC contains the access point image file (such as c1100-k9w7-tar.123-8.JA.tar for a 1100 series access point) in the TFTP server folder and that the TFTP server is activated.
Step 3 Rename the access point image file in the TFTP server folder to c1100-k9w7-tar.default.
Step 4 Connect the PC to the access point using a Category 5 (CAT5) Ethernet cable.
Step 5 Disconnect power from the access point.
Step 6 Press and hold the MODE button while you reconnect power to the access point.
Step 7 Hold the MODE button until the Radio LED turns red (approximately 20 to 30 seconds) and then release.
Step 8 Wait until the access point reboots, as indicated by all LEDs turning green followed by the Status LED blinking green.
Step 9 After the access point reboots, reconfigure it using the access point GUI or the CLI.
HTH