You add a block to a page and something stops it working. What diagnostics should you do before contacting the developer for support or, for free blocks, posting for help on the forums?
The more quality information you can provide, the more likely we will be able to solve your problem quickly.
The tips below are by no means complete. Almost every problem has its own unique foibles. So think of this as a framework within which you can get started.
Clear the concrete5 cache
Dashboard > System & Settings > Optimization > Clear Cache. While you are there, maybe also turn the concrete5 cache off (and make a mental note to turn it on again later!)
Clear the browser cache
Browsers keep local copies of many files and don’t always notice that the file your web site is serving has changed. So clear the browse cache to make sure you are seeing the latest. This varies between browsers, but hitting F5 or CTL+F5 a few times usually does the trick.
Turn off pretty URLs
Dashboard > System & Settings > SEO & Statistics > Pretty URLs. Sometimes pretty URLs need a bit more work that the default .htaccess and config/site settings to work cleanly/
Try another browser
Sometimes problems are specific to a browser, particularly if you are using Internet Explorer. Try a different browser and see if the issue is the same, different, or does not exists. That doesn't mean it is not a problem, but it is important information when trying to solve it.
Check the developer console
Check the php error log
Php keeps a log of any script errors in a text file, usually called something like php-errors.log. Have a look and see if php has reported any errors.
Turn on concrete5 debug
concrete5 has an option to show errors directly on the page. This is by no means as thorough as the php-errors.log and doesn't show all errors that are recorded in the log. See Dashboard > System & Settings > Environment > Debug Settings.
Check the concrete5 log
concrete5 keeps an internal log that some errors are reported to. See Dashboard > System & Settings > Environment > Logging Settings and Dashboard > Repors >Log.
Check the directory path
Block controllers must map exactly from the Camel Cased directory path. The directory the block is in must be all lower case with underscores. The block controller class name must be map to the camel cased variant of that as per Creating a New Block Type.
Try another page
Create a new page and add your problem block to the Main area of it. Do you still get the error?
Try a default theme
On the problem page (or the new page above), change the theme to a default theme such as Greek Yogurt or Plain Yogurt. Do you still get the error?
Try a default template
Many blocks come with alternate templates. Is it the default template or an alternate template you are having problems with? What happens when you swap to the block's default template?
Check the support pages
All marketplace blocks have support pages. Many issues have already been solved for others, so check back through the support pages and make sure you tick the check box to ‘Show Archived’ so you can see problems that were solved more than 2 weeks ago.
Check the support forums
All marketplace blocks also have their own forums (sometimes called Discussion or Questions on older addons). Again, your problem may also be solved if you look back through these pages.
Take some screen shots
Screen shots will help eliminate misunderstandings on just what is going on by making it possible for others to see what you are seeing. Ideally, Take a shot of the block settings in the edit dialogue, take a shot of the page in edit mode so the developer can see the block in context, then take a shot of the published page.
Many screenshot utilities like Awesome Screenshot allow you to quickly mark up a screenshot with red arrows and text to add further explanation.
Contacting the developer
If in doubt, contact a developer by a support request. Just posting to a forum may not get noticed. Sending a PM could get overlooked or lost. Posting a support request makes it easy for a developer to check any issues they need to respond to and keeps everything about the issue conveniently in one place.
Make sure that as well as a description of your problem you include the results of all the tests above.
Support requests also provide environment information and you can attach screenshots.
Revert the page version.
To get your page working again, even from really bad looking errors, you can usually revert the page version from the dashboard. Go directly to the dashboard site map, locate the page, approve a previous version and delete the failing version. The direct URL will be something like http://www.yoursite.com/index.php/index.php/dashboard/sitemap/.