I can only find one similar post to this from December 2017. I would suspect DLL corruption initially.
I would suggest performing a full shutdown of your computer, for starters. https://www.isumsoft.com/windows-10/2-ways-to-perform-a-full-shutdown.html
Personally I find the command prompt method a touch more reliable and easier.
Wait 10 seconds after the shutdown is complete, then power on normally.
Skin color coupons are typically sold from the cash shop. I don't recall any events that have given out skin color coupons, so if there have been events there hasn't been many.
You can buy maple points using mesos through the meso market; in any town, use the Quick Move button and click on the lady in the pantsuit. Enter your PIC and you'll be able to purchase maple points at a rate decided by an average of the rate in your server. The meso market is not available on Reboot, however.
An issue where disconnecting during certain parts of Act 2 in Monad caused a character to become stuck will be fixed. Use the portal in Base Camp, and select 'Act 2'. You will be asked if you want to return to where you were.