Thanks, Bruce
The challenge token file is not being created but I have found it has nothing to do with the entry being a subdomain. As a dummy primary domain, externaltest.com didn't generate the file either. A few other things I have tried include running the server app 'As administrator' and testing the to see the acme-challenge folder can be written to. If you don't see the problem here, we may need to do a team viewer session. Thanks again.
The full log is below and below that the complete TRACE
[ 4/10/18-13:24:45] The URL for the Fetch command was blank
[ 4/10/18-13:24:45] Notify Server Challenge is Ready
[ 4/10/18-13:24:45] LE Server will now fetch
http://externaltetst.com:80/.well-known/acme-challenge/[ 4/10/18-13:24:45] Challenge Token Saved C:\CJR Dev Projects\ResWebC10\web\.well-known\acme-challenge\
[ 4/10/18-13:24:10] Authorize Request externaltetst.com
[ 4/10/18-13:24:10] Registering Account Madrigal Soft Tools Inc. at
https://acme-staging.api.letsencrypt.org/acme/new-reg[ 4/10/18-13:24:09] Server Response When GettingDirectory 200
[ 4/10/18-13:24:09] Time to update the certificate
[ 4/10/18-13:24:09] C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.crt does not exist
[ 4/10/18-13:24:09] Dates: resschedtest.com From:19 MAR 2018 To:17 JUN 2018
[ 4/10/18-13:24:09] Created C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.csr
[ 4/10/18-13:24:09] Created C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.key
InitSideBySide failed create an activation context. Error: 1814
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] Created C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.key
InitSideBySide failed create an activation context. Error: 1814
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] Created C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.csr
InitSideBySide failed create an activation context. Error: 1814
[st] Mar 19 21:16:28 2018 GMT
[st] Jun 2=17 3=21:16:28 4=2018 5=GMT
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] Dates: resschedtest.com From:19 MAR 2018 To:17 JUN 2018
[st] [netTalk][thread=1] not exists C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.crt
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] C:\CJR Dev Projects\ResWebC10\certificates\externaltetst.com.crt does not exist
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] Time to update the certificate
[st] [netTalk][thread=1] NetAcme.PageReceived self.state=1
[st] [netTalk][thread=1] NetSimple.ErrorTrap 0 Server Response When GettingDirectory 200 NetAcme.PageReceived
[st] [netTalk][thread=1] [ 4/10/18-13:24:09] Server Response When GettingDirectory 200
[st]
[st] [netTalk][thread=1] NetAcme.PageReceived self.state=1
InitSideBySide failed create an activation context. Error: 1814
InitSideBySide failed create an activation context. Error: 1814
InitSideBySide failed create an activation context. Error: 1814
[st] [netTalk][thread=1] [ 4/10/18-13:24:10] Registering Account Madrigal Soft Tools Inc. at
https://acme-staging.api.letsencrypt.org/acme/new-reg[st] [netTalk][thread=1] NetAcme.PageReceived self.state=2
InitSideBySide failed create an activation context. Error: 1814
[st] [netTalk][thread=1] [ 4/10/18-13:24:10] Authorize Request externaltetst.com
[st] [netTalk][thread=1] NetAcme.PageReceived self.state=3
[st] [netTalk][thread=1] NetAcme.HTTPChallenge
[st] [netTalk][thread=1] [ 4/10/18-13:24:45] Challenge Token Saved C:\CJR Dev Projects\ResWebC10\web\.well-known\acme-challenge\
[st] [netTalk][thread=1] [ 4/10/18-13:24:45] LE Server will now fetch
http://externaltetst.com:80/.well-known/acme-challenge/[st] [netTalk][thread=1] NetAcme.ChallengeReady :: URI=
InitSideBySide failed create an activation context. Error: 1814
[st] [netTalk][thread=1] [ 4/10/18-13:24:45] Notify Server Challenge is Ready
[st] [netTalk][thread=1] NetSimple.ErrorTrap -15 The URL for the Fetch command was blank NetWebClient.Fetch
[st] [netTalk][thread=1] [ 4/10/18-13:24:45] The URL for the Fetch command was blank