Yeah, we saw this over a year ago on some user-written reports. Customized stock reports are all fine, unless you add another non-Sage parameter.  I suspect it's because Sage reports like to have string parameters.  Look inside any xxRPT.INI, even dates are YYYYMMDD strings.

Thanks for confirming, Jay.  I had one last year and two in the last 2 months.  But my date parameters are working fine; it’s just numbers.  I usually use real date parameters for user input, and then convert them to numbers before using them for selection criteria.  But I can still take a date parameter and pop it onto the report, and it runs fine.  If i do that with a number parameter, even if there is no other reference to it in the report, that’s enough to cause unspecified error.

I have had many reports have this after upgrading Sage. For us we had reports with parameters for period and they were set to a number. The fix was to change this to string and then in the formulas change it back by using  ToNumber

Interestingly this isn't just a Sage 300 issue.  I have been making the same changes but it turns out custom reports with numeric parameters used within Sage HRMS 2017 with recent quarterly updates are facing the same issue.   It's got to be a change in the crystal viewer.   Any idea if a crystal runtime patch might clear this up?

See Sage KB 94509, about installing Crystal Runtime 24 to fix this issue.

Update:  wrong KB & patch; please disregard.  Leaving the message here so that Tim's makes sense following.

I installed and tested CR sp24 in one of my Sage 300 v2020 vm's and it did NOT resolve the issue.

I continue to get "Crystal Report Windows Forms Viewer" with "Unspecified Error" when running custom reports with numeric parameters from the Sage 300 desktop.

p.s.  the kb article only refers to resolving the issue with default printers in terminal servers at this point.

Sorry Tim, my mistake.  I had both issues at around the same time and was thinking this was the Crystal fix.  But i don't think there is a Crystal fix yet for the numeric parameter issue.  Sorry to have put you through the exercise with sp24.

For me the fix was changing the parameters in the report to a string, and then in the formula use tonumber({fieldName}) . It seemed to happen when we were reporting on fiscal period mostly. 

Yes,  I've been doing that for months with sage 300 and Sage HRMS clients as they upgrade but it's not really a fix, just a work around to mask the crystal bug!