Make sure you're using the correct version of impactor, I did this and when I re-signed the .ipa mine would open and immediately crash. It was crashing because I was using an older version of impactor that I had on my computer already.

1. Delete the app

2. Redownload impactor

3. Redownload Yalu

4. Install yalu through impactor

5. Go into settings and trust the profile

6. Clear all background apps,

7. Hard reset (power and volume down for i7 / power and home button for everything not i7)

8. Open mach_portal

9. Profit

If it doesn’t work at the first time, you may need to do it as the the steps several times.