Trade show lead follow-up is killing me - 4 weeks on, still no replies from NPE booth scans

Just got back from a plastics show in the US and I'm drowning. Scanned around 180 badges over three days at our booth, mostly injection molders and Tier 1 auto buyers. Sent personalized follow-ups within 48 hours like everyone says to do, then a second touch at day 10 with our mold flow case studies. Crickets - maybe 6 replies, one real RFQ. Here's the thing: conversations at the booth felt warm, lots of "send me your capability deck" and "we have a project in Q3." Now nothing. I've tried WhatsApp for the ones who gave numbers, LinkedIn for the rest, even had our US rep call two hot ones - straight to voicemail. Is this normal after NPE or am I doing the follow-up wrong? Do you segment by booth chat quality or blast everyone? And what's your realistic reply rate - because 3% is making me question the whole booth spend for next year. Any scripts that actually get molders talking would help.