Hello,
Spark 3.0b9 and 3.1b2 are unable to check for updates because they contain broken links.
The problem is that https://www.shadowlab.org/ has been reorganized, and the links within Spark don't point to valid web pages any more. The fix is to release a new version of Spark with updated links, or to restore the old web pages on www.shadowlab.org.
There is another related bug on www.shadowlab.org. The page at https://www.shadowlab.org/softwares/spark.php has a link to the "additional Plugins Page". That page no longer exists.
On another note, thank you for this wonderful little program! It's a gem.