So my wife and I believed we forgot to sign it by pen (as we thought electronic was sufficient). I contacted IRCC when we realized this and we sent a letter to the same office (Syndey) and I provided my information such as name, DOB, Place of Birth, when I became a Canadian Citizen, my Citizenship Certificate number and Receipt number for the application. This was since we didn't have our UCI and application number as of yet. We included the signed form as well and stated that IF we did in fact sign the original application form, then to simply ignore the one included in this new package.
Since our application is in progress (AOR, medical request, transferred to Mississauga, etc), I would assume that this secondary letter was enough, or we really did sign the original... Sorry, I know it's not a guaranteed solution, but just explaining our situation and what we did, that may have worked.