are you using wtfast? if you're using wtfast, its normal that you can't connect because sometimes its not working. Try to use other servers in WTFast but if you're not using wtfast, I think your internet connection has a problem on connecting in InfinityMU. Try to restart your pc then restart your modem too
Try disabling your anti-virus or add InfinityMU client in exception list,
Sometimes, anti-viruses detects main.exe as unsafe, that's why it automatically quarantine it which can be cause of connecting problems.
As additional, use CCleaner for cleaning and optimizing your PC to make your PC faster and more secure.
Download it here: https://www.piriform.com/ccleaner