Can't get audio sermon to play

We're new to SermonSpeaker, and fairly new to Joomla! Running the latest Joomla! 3.8.3. Our office admin, who runs the web site, installed SermonSpeaker and followed the instructions, setting up one sample sermon. All looked fairly good (subject to eventually adding more description): the menu item Sermons brought up the only sermon. But it does not play. What the user sees is this:

Sermon, November 26, 2017
{tx_mp3gallery}262017.mp3{/tx_mp3gallery}

I am guessing that we need to set up a player, either through Joomla! or through Cpanel, but I am not sure how to do that. All advice most welcome.

Yes, you need a player which works with SermonSpeaker. If you have a look at www.sermonspeaker.net/download.html and scroll down you find a section "Player Plugins". If you're only using mp3 files, the Pixelout player is a nice one.
Install and activate at least one of those player plugins and check its settings.

On another note there seems to be already some audio player plugin installed. At least there is a tag around the mp3 which doesn't come from SermonSpeaker itself. The tx_mp3gallery is a reference to www.themexpert.com/joomla-extensions/xpert-mp3-gallery I think. It may be that this plugin scans the content or each mp3 file and tries to load a player for it. Try disabling it for a check to see if that changes anything.

Thanks for the quick and helpful reply.

Our admin had installed several modules trying to get something to work, when we could not get SermonSpeaker working. As you suggested, one of them was the mp3-gallery one. I uninstalled it, disabled several others, and installed PixelOut. I now get this message when I try to play a sermon:

Sermon, November 26, 2017
{mp3}sermonnow262017.mp3{/mp3}
{tx_mp3gallery}262017.mp3{/tx_mp3gallery}

Somehow the uninstalled plugin seems to still be affecting playback. I do briefly see a black horizontal bar which might be an MP3 playback control, but it vanishes almost instantly.

I have cleared browser cache, restarted, and reloaded the browser.

Yes, it looks like there still is something weird happening.
Can I have a look at the site myself? If you give me the URL I can maybe figure out more.

It is a pleasure to have direct help from the developer.

The site is kuc.ca for Kanata United Church. It uses the Salient theme from RocketTheme and is mostly built from their modules.

Because I did not build this part of the site I am not 100% sure how it connects to SermonSpeaker. I will be trying to find that out today.

That may be the root of our difficulty. There may be a more direct way to use your features.

More info. In Sermons options it is set to Use Plugin. We have the PixelOut plugin installed as suggested but I am not clear how to select it as the plugin to use. Also the Options appear to be related to Flash. Do we need to install Flash on our web host server?