Final update: Within 15 minutes of sending my credit union's tracing number for the ACH transaction to WISE via email, WISE rep responded that '......I can see your money has already reached us.' Transfer is back on track and will be paid out today, a week after I initiated the transfer.
I was "guaranteed" an exchange rate of 35.88 and the rate has dropped since I initiated the transfer (today it's 35.62). I don't know if WISE was slow-rolling my transaction because of that (I'd like to think not) or if it simply got "lost in the shuffle" (again, I'd like to think not.)
Whatever the case, it's unsatisfactory service that appears to have been resolved, though I remain unconvinced that WISE was being entirely truthful when claiming they had not received the money.