Why do I have to submit monthly readings now I’m in a smart meter?
Because smart meters with bulb don’t work! Have a read through the forum and it is flooded with the same complaints.
Per the comment from @darryl5653, they don’t work (in many cases) but the only way to be sure is to ask Bulb to confirm. If this is the case then read the thread https://community.bulb.co.uk/discussion/13916/bulb-unable-to-read-the-smart-meter-theyve-installed#latestt and contribute to get their attention.