Message from Ancestry. (11 May 2018)
"Some users have recently been experiencing technical issues when using Ancestry.com. We’re currently undertaking a series of planned system enhancements that may result in intermittent site issues through Thursday, May 31, 2018. Once complete, they will improve site performance and enable more records, more hints, and more connections, making the platform even more valuable for our community. Please know that your data is safe with us. All the work you have done on your trees will be preserved even if you are experiencing some difficulties as the result of this upgrade. We appreciate how frustrating this has been and thank you very much for bearing with us during this period."
If this issue hasn't been resolved by Ancestry by 1 Jun 2018 then contact their support to look at your tree.