When you received the notice is IMMATERIAL. The rule says "sent by the court". Was it sent after the time had expired? That's point one to check.

Second point, paragraph (4) says the charge MAY be dismissed. May is permissive. You can ask the court but they aren't obligated as if the rule said SHALL.

Third point, paragraph (4) further says "upon showing prejudice" which means you have to tell them that somehow the delay has been detrimental to you mounting your case.

That's just the reading of the law. Washington law is quirky (AND YOU'D HAVE GOTTEN A BETTER ANSWER IF YOU HAD FOLLOWED THE RULES AND GAVE THE STATE NAME ORIGINALLY) and one of the Washington state experts will be along to offer specific help once they notice despite the lack of the state being mentioned, we're talking about Washington.