Cant log in but get: ModSecurity: XML: Unable to evaluate xpath expression

Hello,
I have installed NextCloud on a shared server and it went without a hitch. I was able to log in, configure my account and added files. Unfortunately this morning I am unable to log in and get this error when I attempt:
The server was unable to complete your request.

If this happens again, please send the technical details below to the server administrator.

More details can be found in the server log.

Technical details

  • Remote Address: 73.131.93.27
  • Request ID: W729GUWimgcAAKYLOTkAAAAF

Here is the error log o the incident:
Wed Oct 10 00:00:18 2018] [error] [client 75.40.88.108] [client 75.40.88.108] ModSecurity: XML: Unable to evaluate xpath expression. [hostname "link-sky.com"] [uri "/remote.php/dav/files/Skyadmin/"]

Naturally I sent this to my server admins at liquidnet and they said they were not familiar with next cloud but that I could turn mod security on and off. Tried that and neither state helped.

Not sure what could have changed overnight!

Server info:

Operating System:

Debian GNU/Linux

Physical IP Address:

162.210.102.41

Default Route:

162.210.102.41

Sendmail Path:

/usr/sbin/sendmail

Perl Path:

/usr/bin/perl

Perl Version:

v5.24.1

PHP Version:

7.1.22

MySQL Host:

localhost

MySQL version:

5.7.23

PostgreSQL Host:

1.pgsqlserver.com

PostgreSQL Version:

9.6.3

FYI- The desktop app works fine on my Mac, just not able to log in in browsers. I am grateful for any help. I cant even find information about the error anywhere. 
Seems like this is a server error so perhaps you can help me guide them? Thank you very much in advance!! Ken