I saw it twice, thought it was totally charming, hilarious, & had great special effects. I’ve read the first four books, saw the BBC TV series, listened to much of the radio series- all in the mid/late-80s, but havent come back to them in years. Hence, I’m not a fanboy or a purist, but a nostalgic admirer. I found the romantic comedy aspect totally appropriate (it struck me as the main divergence from the originals). Both times I went, I was with people who had only slight knowledge of it & they were thoroughly entertained.
So if it did flop, what went wrong?