This has happened to me. After a few tries I gave up and found a different system. At the time I assumed it meant that another CMDR had already purchased a claim but hadn't deployed beacon yet, or perhaps the system tick needed to happen, but as you've now already waited with no change, those explanations now seem unlikely
For anyone needing more context:
You go through the colonization claim purchase as normal, click the final buttons and confirmation to complete and process your claim, then the colonization menu closes as if you succeeded (while staying in map view), but for just a few seconds elsewhere on the screen there is a red box in the bottom right corner saying "colonization failed". I didn't even notice it the first time, and it took me a while to figure out that my claim had NOT in fact been processed, despite the confirmation button being clicked. I tried a few times and there was no clue that I could find why it wasn't working, and the error message has no other information.