Looks like your ISP agreed that your IP address was used in the past to send some spams, and great that they accepted to change yours.

Actually my ISP never acknowledged that the IP address had ever sent spam and I have no reason to think it was. Since I have had no problems with any other website blacklisting me - now or in the past 15 years - it seems equally likely that my IP address was flagged in error by this forum's software. At first I tried to access the forum through a VPN which worked once - then all the VPN addresses were blacklisted as well. Then I resorted to accessing this forum via my cellular data connection - then that was blacklisted. In the end, I had to remote access a family member's computer in order to post this thread. WTF? All I was trying to do is learn how to use this software (only to realize in the end the basic functionality I was seeking doesn't even exist in SH3D).

In the end I've decided to abandon SH3D in favour of paid software after learning how many features and functions SH3D lacks (the lack of precise wall locationing and the lack of front elevation views sealed the deal).