Thanks for asking and sorry for the trouble you are facing.
As you have done most of the basic troubleshooting, I suggest you to please make sure that the PHP you are running on the server if above 7.0. As per the requirement guideline, minimum PHP required to run WordPress is 7.0.
As you are not comfortable in sharing login details it's difficult for us to troubleshoot. We have listed few other troubleshooting steps that you can take a look in following tutorial.
That's being said can you please share a screenshot of the dev tools console? Maybe we can get some clue from there if there is any error message showing up. I have recorded a screencast that you can take a look to open up devtools and the error message section. https://cloudup.com/c6UrjABYNWC