You can have a maximum of three 4K devices under one account Sony Entertainment Network™ (SEN) account.
The error Looks like you have too many 4K devices using the same account. You can have a maximum of 3 4K devices under one account. appears and the 4K player will fail to connect if a fourth device is attempted to be used.
NOTE: Visit the SEN support website for SEN account assistance if you feel that this connection error appears incorrectly.