I can't find any promos for What's Happening Now!! on YouTube, which is usually surprisingly easy for syndicated sitcoms from the '80s. I did find this print ad online though:
https://pbs.twimg.com/media/DmiW3shU0AAxs9G.jpg

And the Radio Discussions site, has numerous (https://www.google.com/search?biw=1600&bih=740&sxsrf=ACYBGNQFDcTvYseintzo_lQZeH75_dCmng%3A1568627716187&ei=BFx_XbfcCsP6sAX7z5jQCw&q=What%27s+Happening+Now+1988+site%3Aradiodiscussions.com&oq=What%27s+Happening+Now+1988+site%3Aradiodiscussions.com&gs_l=psy-ab.3...6544.7454..7811...0.0..0.117.530.1j4......0....1..gws-wiz.OVTg2Q_8p9I&ved=0ahUKEwi37rrOidXkAhVDPawKHfsnBroQ4dUDCAs&uact=5) old (https://www.google.com/search?biw=1600&bih=740&sxsrf=ACYBGNQub3uUqidc2Ap7O3IKz3oOJcY-_w%3A1568627725094&ei=DVx_XdSnBcP2swXHtY74Bg&q=What%27s+Happening+Now+1987+site%3Aradiodiscussions.com&oq=What%27s+Happening+Now+1987+site%3Aradiodiscussions.com&gs_l=psy-ab.3...64005.64570..64948...0.0..0.118.235.0j2......0....1..gws-wiz.ku7bE5QNDnA&ved=0ahUKEwiU4trSidXkAhVD-6wKHceaA28Q4dUDCAs&uact=5) schedules (https://www.google.com/search?biw=1600&bih=740&sxsrf=ACYBGNRuF8AoXv-BNNlnCd0PmBtPT6Tgpg%3A1568627791066&ei=T1x_XbnXA8yMtgX22oeYAg&q=What%27s+Happening+Now+1986+site%3Aradiodiscussions.com&oq=What%27s+Happening+Now+1986+site%3Aradiodiscussions.com&gs_l=psy-ab.3...13962.14409..15110...0.0..0.117.229.0j2......0....1..gws-wiz.bg5-Zq9bPp4&ved=0ahUKEwj5upXyidXkAhVMhq0KHXbtASMQ4dUDCAs&uact=5) that list (https://www.google.com/search?biw=1600&bih=740&sxsrf=ACYBGNSya1io-bsTvbUlesgaynkyAnt6Eg%3A1568627807531&ei=X1x_XcaCIIfaswXk14CADA&q=What%27s+Happening+Now+1985+site%3Aradiodiscussions.com&oq=What%27s+Happening+Now+1985+site%3Aradiodiscussions.com&gs_l=psy-ab.3...14342.15096..15489...0.0..0.155.287.0j2......0....1..gws-wiz.O15NOAjKYaQ&ved=0ahUKEwiGroL6idXkAhUH7awKHeQrAMAQ4dUDCAs&uact=5) the individual stations across the country to have aired WHN.

WHN premiered on September 7, 1985 at least in New York on WNEW-TV Channel 5 Saturdays at 5:00PM followed by Small Wonder at 5:30PM.

I know I have my original recording from the same day Small Wonder premiered with commercials, I believe i recorded the entire premiere hour of WHN & Small Wonder with commercials on September 7, 1985 on WNEW-TV Channel 5 NY 5:00PM-6:00PM.

The original VHS is in the archives somewhere.

Hope that helps in your research

WHN premiered on September 7, 1985 at least in New York on WNEW-TV Channel 5 Saturdays at 5:00PM followed by Small Wonder at 5:30PM.

I know I have my original recording from the same day Small Wonder premiered with commercials, I believe i recorded the entire premiere hour of WHN & Small Wonder with commercials on September 7, 1985 on WNEW-TV Channel 5 NY 5:00PM-6:00PM.

The original VHS is in the archives somewhere.

Hope that helps in your research

What I have thus far (https://en.wikipedia.org/wiki/What%27s_Happening_Now!!#Broadcast):
City Station

Atlanta WGNX 46
Baltimore WBAL 11
Bloomington WYZZ 43
Denver KWGN 2
Detroit WKBD 50
Green Bay WGBA 26
Greensboro WMYV 48
Hartford WTIC 61
Kansas City KZKC 62
Los Angeles KTLA 5
Manchester WMUR 9
Miami WBFS 33
Mobile WPMI 15
Nashville WZTV 17
New York WNEW 5
Orlando WOFL 22
Philadelphia WTAF 29
Sacramento KTXL 40
San Francisco KBHK 44
Seattle KCPQ 13
Spokane KSKN 22
St. Louis KDNL 30
Washington, D.C. WDCA 20