Tag Inactive for Call Only Call Tracking

Google Ads has a red error for all my CTM clients for the "Call Only Call Tracking" as Tag Inactive.

As I think it through, there need not be any tag on the website because this number is considered an 'off-site' source.  The conversions are correctly returned to Google Ads as appropriate, but using the number doesn't ever record a click to the website, so I'm not sure why a tag would need to be present.

Am I missing something here?  I've gone around a couple times with off-shore Google Reps and CTM staff, but have never come to a satisfactory answer.