What it means
てからでないと means that the action in the first clause must be completed before something in the second clause can happen. It expresses a prerequisite and usually introduces a negative, impossible, or undesirable result, such as “cannot,” “will not,” or “must not.” The construction emphasizes that the first action is required before proceeding, rather than simply describing the order of two events.
Usage note
The clause after てからでないと is normally negative or expresses an unfavorable result. Do not usually use this construction for a simple positive result; use てから or その後で when you only want to say that one event happens after another.
How to use it
Verb (て-form)からでないとClause
申請してからでないと、利用できません。
Unless you apply first, you cannot use it.
Verb (て-form)からでないとClause
申請してからでないと、利用できない。
Unless you apply first, you cannot use it.