Getting lost accounts to respond to an outreach - help

My "project" is to take a list of "lost accounts" (all stage 1 or 2) and re-engage them in a non-salesy conversation. Objective is to build a trusted relationship so when they're ready we'll be top of mind.

I've tried email, LI, Gift cards to a charity and starting out bound calls. A few have engaged and we've had great conversations that were honest, non salesy, non marketingy. The rest are just not responding.

Any advice or ideas. B2B companies, mid level managers and some directors, mostly in prof svcs industries.

Thanks