Not sure of it was when they launched but as of now you are only allowed to use the free plan for... 30 minutes.
This is never mentioned on their pricing page, where they carefully list all the free plan details, except this one...
The free plan never expires. The 30 minutes of credits you are referring to are bonus credits which let you remove the watermark. After they expire you can continue using the app 100% free with our watermark. If you would like to remove it, you can buy hourly credits or a monthly subscription.
SYQEL is an amazing platform! I love the visualizations and use them with my music whenever I can. It has great benefits and I love everything about it.