Problems with the onlne Combine tool

Dear Adobe, 

I am an Adobe free user and I want to use the online combine tool to merge my pdfs. However, it seems to have a problem as it always shows "Unable to process request" and asks me to contact Customer Support. 

I have read the previous similar question about this particular problem. However, this happens to any documents I have tried so far and it's been days since the last time I used the tool online. 

Could you help me with this?

Thank you very much!

Sincerely.