The new IOTA wallet released just now has an option in the Tools menu to begin the recovery process for people who have had issues with 0 balance lately.
The recovery process is split in two parts. The second part to the process will be made available soon.
In part one, you first have to input your original (old) seed into the recovery tool, then a new seed. Make sure it's a brand new seed, completely unused. Then submit and wait for the process to complete.
Get the new IOTA GUI wallet with Recovery Tool (Phase 1/2) here:
https://github.com/iotaledger/wallet/releases
More information on the official IOTA blog here:
https://blog.iota.org/gui-v2-5-2-latest-release-with-iota-reclaim-tool-32d364d6241a