Adolf, this solved it for me, for any reason
# pakfire remove pmacct
PAKFIRE INFO: Packages to remove:
meta-pmacct 100.00% |=============================>| 1.05 KB
PAKFIRE INFO: pmacct - 500.00 KB
PAKFIRE INFO: Is this okay? [y/N]
PAKFIRE REMV: pmacct: Decrypting...
pmacct-5a5e272-7.... 100.00% |=============================>| 485.24 KB
PAKFIRE REMV: pmacct: Removing files and running post-removing scripts...
PAKFIRE REMV: pmacct: Finished.
Now pmacct is listed under available packages and I could reinstall it the proper way.
Nevertheless, the package was not showing up under installed packages in WebIF!