RaspberryPI NextCloudPi Docker - Problem Loading Page

Question

I'm trying to follow these steps to get a docker container running NextCloud on my RaspberryPI. The steps seem very straight forward except I can't seem to get this working. The biggest difference is that I want to use an external drive as the data location. Here's what's happening:

I run sudo docker run -d -p 4442:4443 -p 442:443 -p 79:80 -v /mnt/nextclouddata:/data --name nextcloud ownyourbits/nextcloudpi-armhf

but when I go to https://pi_ip_address:442/activate (or any of the other ports), I get "problem loading page". I've also tried using https://raspberrypi.local:442/activate as well as appending both the IP and the name to the end of the command (where the DOMAIN is listed in the instructions).

I've seen some posts talking about how this is a problem with how docker accesses mounted drives, but I can't seem to get it working. When I type sudo docker logs -f nextcloud I get the following errors:

/run-parts.sh: line 47: /etc/services-enabled.d/010lamp: Permission denied
/run-parts.sh: line 47: /etc/services-enabled.d/020nextcloud: Permission denied
Init done

Does anyone have any steps to help get this working? I can't seem to find a consistent/working answer.

Thanks!