Depending on the phone model, the way to solve it is different.
Please kindly follow the steps below.

iPhone

1. Please check the APN setting to see everything has been filled in correctly.
For more information, please visit https://www.sakuramobile.jp/apn-settings_travelsim/

2. If you have done the above, and it is still not working, please kindly try the following.
・If you are using an eSIM at the same time.
=> Erase the APN setting
=> Turn OFF the eSIM
=> Restart the phone
=> Do the APN setting again before you turn on the eSIM

・If you are only using our SIM card.
=> Do a NETWORK RESET for your iPhone
=> Restart the phone
=> Do the APN setting again
※ How to reset network settings : https://support.sakuramobile.jp/hc/en-us/articles/4415185455257--For-iPhones-How-do-I-delete-existing-profile-or-reset-network-settings-

Android phone

1. If you have a dual SIM card model, make sure you only insert our SIM card.
※ If you would like to have both SIM cards inside your phone, then please complete all the steps before you do the set up for the second SIM card

2.Please check the APN setting to see everything has been filled in correctly.
For more information, please visit https://www.sakuramobile.jp/apn-settings_travelsim/

3. If you have done the above, and it is still not working, please kindly try the following.
・Attempt a NETWORK RESET (different model have this function is different menu)
※ Please do not do any other reset
・Restart your phone
・Do the APN setting again

If you have attempted the above, but still does not work, please send 4 things to our email for further help.

Our email address : contact@sakuramobile.jp
・A screenshot of the APN setting page, we would like to see if everything is correct.
・A photo of the SIM card, we would like to know the number on the back of the SIM Card.
・The phone model
・The booking ID for this product