Sermon Manager - Unable to Create New Sermon

SermonSpeaker version 5.6.2, Joomla version 3.7.2. When I click New on the Sermon Manager screen to input a new sermon, my screen goes to a white page and nothing else happens. The address in the top bar is my website address/administration, then the following. It looks like it is redirecting but nothing happens. It seems to have happened after the last Joomla upgrade? It was working fine before that.

/administrator/index.php?option=com_sermonspeaker&view=sermon&layout=edit

A whitescreen usually means there was a fatal server error.
Which PHP version are you using? And can you enable error reporting in the global Joomla configuration and see if an error is shown? If not, you will have to ask your hoster so he can check the error logs.

PHP version 7.0.19. The following are the error messages I'm getting when I turn on error checking. I can't reach the developer and I was trying to fix it on my own but I don't understand where to check for these or what they really mean other than what I read on the web.

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; plgSystemCSSConfig has a deprecated constructor in /home/MYSITE/public_html/plugins/system/cssconfig/cssconfig.php on line 29

Deprecated: Methods with the same name as their class will not be constructors in a future version of PHP; Color has a deprecated constructor in /home/MYSITE/public_html/templates/rt_oculus/features/color.php on line 11

Deprecated messages mean the respective code is marked for removal in a future version of PHP. However it should not generate a fatal error as it is still supposed to work fine in your version.
There is likely something else messing up.

You could try disabling non-core plugins (especially system and content ones) and see if that solves the error. If it works, enable one plugin after eachother and try each time. When it breaks again, you have the culprit.