Nextcloud is not working after Upgrading Ubuntu to version 18.0.2

Hello there,
I am a novice. I had nextcloud up and running on Ubuntu 16.0.2. But this morning there was a notification on the screen saying to upgrade Ubuntu. Without thinking at all, I stupidly upgraded it and now Nextcloud isn’t working. I am seeing a message during boot that says “Failed to start Apache…”
Please, someone help. Don’t know much about Ubuntu. Thanks in advance.