How to dismiss the old application from ex

I would appreciate some advice.
After applying for divorce under new rules, I received an email saying that my application is on hold because there is another older application which needs to be dismissed first.
The older application is however from my ex, and was never progressed.
The question is whether I am allowed to apply to dismiss that old application or only the ex can do it?
Thank you in advance.

It depends how old the previous petition is. If it was issued, say, five years ago you could certainly apply to have it dismissed. On the other hand if it is quite recent you would first have to write to your ex and invite him to dismiss it by consent (keeping a record of the correspondence). Assuming he did not co-operate and/or reply you could rely upon the correspondence to show that you had made every reasonable attempt to deal with it by agreement before making an application to dismiss.

Thank you David.
The ex’s petition is 3 years old. I just found a court order from last year that the petition “is stayed”.
Does it mean I still have to make an application to dismiss it or is it the same?

A stay is not the same as a dismissal. You need to apply to have it dismissed before you can issue another application for divorce.