There are 2 issues you have shared.
- MATLAB is asking to login everytime you open it - This might happen due to no valid license files found on the license file search path. Check this link to get more information - https://www.mathworks.com/matlabcentral/answers/106141-why-am-i-continuously-prompted-to-activate-when-i-try-to-launch-matlab
- Using MATLAB without internet connection - MATLAB and its toolboxes can be run on a computer without Internet access. Check these links to get more information -