It turns out that Dropbox has restricted account linking to 'up to 3 devices'

By answering Q & A questions in the Help Center, Dropbox found that from March 2019 the number of devices tied to an account was limited to three.

Is there a limit to the number of devices I can link to my account? – Dropbox Help
https://help.dropbox.com/account/computer-limit

Dropbox adds three-device limit for free users-The Verge
https://www.theverge.com/2019/3/14/18265574/dropbox-3-device-limit-free-accounts-plus-professional

The Dropbox announcement is drawing attention because IT media Liliputing posted on Twitter.

But if you have more than three computers, phones, or whatever, you can still unregister a device to add a new one-it's just going to be a Dropbox user with a free account can now only link up to three devices to Dropbox. pain for multi-device folks. https://t.co/VubadTN6eF

— Liliputing (@liliputingnews) March 12, 2019

This description is in the "Help center" tab of the website Click " Manage my Dropbox account " ...

Open the tab "Manage multiple devices" and click "Is there a limit to the number of devices I can link to my account?" It is ahead of you ...

What exists as the answer to the question. In response to the question, Dropbox has answered that "The basic user will have a maximum of 3 devices from March 2019."

According to Dropbox, users who had tied three or more devices prior to March 2019 will continue to be able to use the services on those devices. However, even if you buy a new computer or smartphone, you can't get a new string. If you want to link 3 or more devices with your account, you need to change to the paid version "Dropbox Plus" or "Dropbox Professional". In addition, price price of 1200 yen / month, the capacity 2TB of Dropbox Professional in Japan of capacity 1TB of Dropbox Plus and 24,000 yen / year has become .

Note that Evernote also has a two-device limit, and Dropbox is expected to encourage users to transition to a premium plan by limiting the number of devices.