There can be several reasons why your board is stuck in a mode, and each mode may indicate a different resolution. 

Start with the Remote Concerns article to ensure it's not the remote keeping you from changing modes.

SAFE

SAFE mode is the first mode entered and pressing either mode button should go to the last used mode. 

If the board drops back to SAFE mode mid-ride or you can't leave SAFE mode, this generally indicates that the board is recognising a concern, this can be confirmed in the Board Errors article.

SLOW

Being stuck in SLOW mode will usually relate to a battery communication concern, this can be confirmed in the Board Errors article.

ECO

The board will drop back to ECO mode mid-ride when it reaches a certain voltage, but it can also be a result of a motor controller communication concern.

If the board is charged and you cannot leave ECO mode, refer to the Board Errors article.

If these do not alleviate the concern, we recommend contacting our tech support team.