Without knowing more about your problem and the input data to your PROC GLIMMIX code, I can only offer a few general suggestions:
1. If you cannot obtain proper convergence for the specified model, you may need to consider fitting a simpler model, that is, a model with fewer parameters. Looking at the model below, a considerable number of parameters may be associated with the random effects that need to be estimated.
2. While convergence cannot be guaranteed, you may want to try altering the default optimization options available in the NLOPTIONS statement. See the NLOPTIONS statement description using the following links: SAS Help Center: NLOPTIONS Statement
SAS Help Center: NLOPTIONS Statement: Shared Concepts and Topics
For instance, changing the optimization technique (NLOPTIONS TECH= option) or increasing the maximum number of iterations (NLOPTIONS MAXITER= option) may be helpful. Options for alternative stopping criteria are also available. The options for displaying the optimization history may provide useful information.
For more information, please see the following:
SAS Help Center: Choosing an Optimization Algorithm
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