Hi Angelo and thanks!
The mentioned project giving me trouble is an old one developed back in 2017 and updated with pubcoder up to last year or the year before. Does this help? Do I still need to send link?
I've sent another project (developed with the latest version of pubcoder) and pubreader does work even though for some reason it wouldn't transfer the project via wifi (and the beachball rolls) so I used Airdrop from desktop to iPad.
Thanks for letting me know