Below are some of the factors that may remedy the situation.

1. Please check the maintenance and service outage information of NTT.

NTT East maintenance and service outage information (Japanese)
NTT West maintenance and service outage information (Japanese)

2. Turn off your ONU (Optical Network Unit) and your broadband router, wait for about 15 minutes and then turn them back on.

3. If the status lamp of your ONU or VDSL modem is shown as below, there may be problem with the FLET'S line. Please contact NTT East/NTT West.

ONU:
The lamp for 光回線 (fiber-optic line) and/or
認証 (authentication) is off.

VDSL modem:
The lamp for VDSL or LINK is either blinking or off.
The lamp for FAIL is red.

If the lamps mentioned above are on but you still cannot connect to the internet, or if you are unable to check the lamp status, or unsure, please contact English Customer Support: Technical Support Inquiries.

English Customer Support: Technical Support Inquiries