Hi, Jessie,
Sorry to hear you're experiencing this issue.
The Microsoft Edge functionality and feature availability may vary on older operating systems. To ensure that Microsoft Edge installs correctly, and all functions work correctly, Edge needs a minimum version of the operating system, on Mac is the Catalina (10.15). You can see this information at this link.
https://learn.microsoft.com/en-us/deployedge/mi...
To be able to use Microsoft Edge again you will need to update your version of macOS to Catalina (10.15) or later. You can see how to update macOS on Mac at this link.
https://support.apple.com/en-gb/HT201541
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
I hope this information helps. If you have any questions, please let me know and I'll be glad to assist you further.