Open Tasks and deal owner glitching

Hi there, has anyone experienced an issue with open tasks and deal owner glitches. We can’t work it out, we’ve logged in using different sets and browsers on our work PCs  and these functions no longer work, yet if we log in on personal laptops or PCVs they both work.  The issues are - we can see the task, but if we click on deal - the view completed / view open tasks returns as zero despite there being a task against the deal. Also the deal owner option isn’t showing us our prepopulated drop down lists. Any ideas - we use Edge, tried Chrome - neither work and we have looked at our browser settings, reset our PC profiles - all with no luck!?!