The answer to whether you can repair a window with a seal failure depends on a few factors. Read what they are here.
Firstly, you need to consider the type of glazing. Most double pane insulated glass units have a glazing bead, which can in most situations be removed with the glass and replaced with a new window. If it does not have a glazing bead, it may not be possible to repair seal failures. Warranty is also another factor to consider. If the window is out of warranty, the cost of repairing a window with a seal failure is generally less expensive than an entire new window. However, if your window is heading towards the end of its life, it may be worth investing in a new window as it will be more cost-effective in the long-run. Read more about repairing windows with a seal failure here.