I have launched several app projects in the past and went through what you describe in your question: redefining the primary audience/customer base, a couple of times.

If you have already exhausted the tools and budget available to you to reach out to your first primary target, it may be time.

However since you mentioned "a lot of advertising and reaching out", it may be beneficial to better understand what has been done on what budget so there are learning opportunities for your next campaign.

The points to consider:
• What was your budget?
• Was it effectively used/sufficient to reach your targeted audience?
• What kind of advertising and reaching out did you do?
• Are there other ways that you did not try/were not aware of?
• What percentage of your targeted audience did you actually reach?

Reflecting on what was done will allow you to better craft your next marketing/advertising strategy for the industry you target next (i.e. construction industry). You would be building on the previous strategy as opposed to starting from scratch.

If you have any follow up questions, please feel free to reach out to me. Good luck!