Yes It can happens. But with this limited information hard to guess the the actual problem. Please share more details if possible CAM-B3LYP output file and other error output file.

Attached are two output files, one successful and one failed. All of the BP86 method calculations either do not have initial convergence or eventually find a point that is not within the convergence threshold (10^-8). This failed file is at a def2tzvp level, however this exact same problem occurs at a def2svp level. These Reduced Species calculations employ Restricted Open Shell HF and I have tried using a successful Unrestricted Hartree Fock calculation of the reduced species as the starting geometry as well as the optimised neutral molecule as the starting geometry with no success.

Thanks for your response Debasish

Thanks for sharing the files. I don't have much idea about Ir. I can suggest you to try UDFT instead of RODFT. Check the stability of the wave function (opt=stable) in your successful calculation. Basis set you have used for Ir is all electron basis too large. Try to use first a basis with effective core potential for Ir. Finally you can compute in def2tzvpp using the guess of lower basis calculation.     

Do you use Gaussian? SCF=YQC might be a good solution. Anyway, try to set quadratically convergent SCF algorithms.

I am obtaining values for both UDFT and RODFT to almost benchmark/compare them, I will take into consideration using a basis set with an effective core potential for Iridium, as well as removing and adding terms in the parentheses of the SCF keyword. I did not know about SCF=YQC, that seems like an ideal solution to this problem.

Thanks for all the responses, hopefully I can get some results soon.

I don't know whether you have solved the problem already.

First of all, you are talking about reduced species but in the unconverged file you have charge +2 what should correspond to the oxidized one. Is it ok or a typo?

I would recap what was said before already: use UDFT and play with convergers. For me (I also from time to time calculate heteroleptic iridium complexes in different charged states) usually SCF(Damp, XQC) helps. If this does not help one can think about more sophisticated stuff.