Block not supported errors stem from three main causes: JavaScript syntax errors in the main block file, issues with block registration in JavaScript or PHP, and mismatched block names between registration points.
JavaScript errors break block functionality in the editor while leaving frontend display intact. Registration errors affect both contexts, while name mismatches create complete incompatibility across all environments.
Systematic debugging involves checking JavaScript console errors, verifying registration functions in both JavaScript and PHP, and ensuring block names match exactly between block.json and registration calls.