I have found myself in the same issue today on a Windows machine. I have followed the suggestions in this thread and I am now in a mess.
I have first uninstalled and reinstalled S1, but as stated here it makes not difference.
Then I have uninstalled both S1 and Splice. After that I have reinstalled S1 and I have manage to activate S1 using my personal license key.
After I have have reinstalled Splice back the Activation window is again overwritten by Splice though and I cannot see or select my license any longer.
The last solution proposed here by karlsvegare1 works
Open the C:\Users\-yourusername-\AppData\Local\SpliceSettings\license\ folder and edit the studioone4.lic file with notepad. Remove all the stuff in there and save it. Then right-click the file and check the write protect box. Done. Now you should be able to start Studio One and it doesn't care about splice. win-win.
But it is definitely a dirty hack.
What I find really deplorable is not seeing anyone from PreSonus commenting on this thread. I am a new S1 customer, is this the level of support I should expect to see from now on? If this is the case I already regret my purchase.
Partnering with Splice is a decision that PreSonus has taken and they are not providing a clear solution for this problem? Simply unacceptable!
The most incredible and utterly annoying problem that I have come across though, is that one of the most important VST3 plugins I have, Reason Studios, is not seen anymore by S1. It was working perfectly when I had S1 installed through Splice, but since I have uninstalled and reinstalled S1 the plugin is not found by the VST scanner anymore (I can promise that is still in the VST3 folder, it has not moved an inch from where it was previously).
This has made S1 simply unusable for me.
On top of that also my MIDI keyboard has been reset and now it is appearing with a different name.
I had to reconfigure it completely and this change has affected also other DAWs I have installed like Reaper.
Thank you for your silence and for your acquiescent partnership with Splice that cause all these issue PreSonus.
As new customer I am really impressed!