The proposal keeps moving without you
An owner, a schedule, and a branch on the reason it stalled.
A custom integration proposal is a long, considered, high-consideration document, often revised several times. It goes out, and the client goes silent while they consult four other people.
Nobody owns the next contact, so it ages. The client eventually proceeds with whoever stayed in touch, or reduces the scope to whatever they still remembered from the document.
The sequence
day 0
day 2
day 5
day 10
And when they do reply
Three different problems. One “just following up” message answers none of them.