less than 80% of your list has mapped to your chosen identifier type
DAVID last received an update in May 2016 (https://david.ncifcrf.gov/content.jsp?file=update.html), so any additions to the Gene Ontology database since then won't be present. I checked the examples you posted in Biomart and found that only 2 have GO annotations, so you're likely not missing an immense number of genes. Having said that, you'd be best served to use a more frequently updated tool than DAVID. Around 2015 there was an outcry because it hadn't been updated in 6 years and the database was so out of date that people were getting questionable results. Have a look at one of the many Bioconductor packages for convenient free solutions that are better maintained.